Answer both parts Essay Example | Topics and Well Written Essays - 1000 words

Answer both parts - Essay Example is worthwhile to bring in some free press which would completely rely on the happenings in the society rather than some business news and health updates which can be worthless to the American public. According to ( Hegdon 70 ) â€Å"Abusing a human being is not easy to do; consenting to do it is not something that comes naturally†. Now the issue here is not easy to understand .The author is trying to justify the reason for the harassing among criminals in Guantanamo and it is not easy to defy the author. We know that the prisoners in Guantanamo are not innocent people and bringing out the truth from these vicious criminals is not an easy task. The interrogation and abusing is a part of prison life and it is the way to bring justice to the countrymen. It is shocking to know that these prisoners deserve such abuses but this is the only way the truth will come to surface. Human right is not an aspect which is alien to people of the 21st century .We are humans and we do have the right to live on earth like any other person. Human rights have been a controversial issue since man has civilized. Generally speaking, the human rights issue covers many subjects and it is still an evolving phenomenon. Why is human right a crucial subject? It is because human have varied culture, race, sexual orientation and religion and all these factors need to be considered when one talks about human rights issue. The human right law in American and Africa is not same and to understand the differences it is important to understand what it means to be a human. Human rights give freedom to individual as he has free will and with human rights alone can one nurture a democratic nation. (Thesis) a) Human rights mean no discrimination and this means there is freedom for people to live on their planet which they own. Frankly speaking, human beings have free will and he can only conduct his life on earth with ample freedom. Everyone, despite of their color, gender or race has complete right to

Winning a Lottery Essay Example | Topics and Well Written Essays - 750 words

Winning a Lottery - Essay Example The article's headline says, "Artist Wins Million." Included a picture of your surrounded by your family and friends. Everyone in the picture was smiling. But, the reality is different. With the help of this letter, I want to tell you some negative effects of sudden wealth. But my message is very clear that sudden wealth can bring nothing but unhappiness. It may directly effect on your personality, relationships, and lifestyle.Winning a lottery will create a sense of isolationism and you will be separated from friends and family. This could happen if the winner like you relocated into a new setting; therefore, it will disconnect you from your friends and family. As, what, I have recently experienced in my life. You could furthermore appeal new family and associates who could be characterized as being 'false' as their concerns are in the cash and not in your friendship. For example, there have been normal situations of distant or estranged relations abruptly and unexpectantly seeming out of the azure when hearing of a family member's latest fortunes. Eventually the one-by-one may not be adept to differentiate their authentic associates from the 'false' ones. They may then isolate themselves from all of them or just accept the realization that some of their associates are only actually involved in what the victor can do for them and not the victor themselves. Drastic change is abnormal and thus the one-by-one may not be adept ... There may furthermore be too much force on the individual. There are family constituents, associates as well as economic advisors, all of who have inconsistent and vying interests. This can lead to stress and tension as well as a lesson dilemma for the one-by-one as a outcome of them having to conclude between who they should hear to and take recommendations from. This could finally manifest itself into a pattern of guilt and hostility in the direction of these persons and loved ones. For this cause, the lottery can conceive an painful position for you and you may not have had to make such significant conclusions and choices. This could conceive an unhealthy and dejected state of brain for you that could finally lead to contradictory tendency. However, I would like to state that it is not triumphant the lottery that directs to persons committing suicide, but diverse socio-economic components and variables that are the genuine determinants of suicide. For example, if or not the one-by-one was struck as a progeny or if he/she came from a lone parent family are significant components that should be taken into account as they play a key function in forming a person's mind. The one-by-one could furthermore have been psychologically unstable in the first place. Therefore suicide can not be verified to be exactly associated to triumphant the lottery as the person's psychological state of brain before triumphant is a key determinant. Conclusion All in all, lottery winning will create troubles in your coming life. And you could be more irresponsible and unnecessary with your money than you must be. In the long run, the amount that you have won could be enormously

Development of My Interest in Business Economics Personal Statement - 2

Development of My Interest in Business Economics - Personal Statement Example Availability of land and water, and the region’s blue mountains and waters identify agricultural opportunities tourist attractions. The locality, however, has been isolated from the rest of the world and this informed and motivated me to improve it. My experience from my community and from cities such as Hong Kong and others around the world has also influenced personal and professional goals and determined my choice for business economics as a major. I lived in Wuyuan for the first ten years of my life and witnessed its economic development, which has been significant. The locality has gradually improved its interaction with the rest of the world. Economic activities have emerged and grown, an occurrence that has informed me on the power of economic reforms. Interaction with economic development in Hong Kong, however, challenged me because of its rapid pace and power. It shocked me and influenced my desire to initiate and influence economic development, first for myself and then in my community. My volunteer work experience also identifies my passion for my community. I have been volunteering in USC Pacific Asia Museum on the second Sunday of each month for the last few years. This has informed me on Asian history that I have also taught children. I am also a member of John Chinese Young Volunteers Association. At Pasadena City College, I am a member of business club, economics club, global club, Helping Hands Club and International Socialist Organization club in which I share my ideas on communal empowerment. As part of my community initiative, I will send some clothing, together with defective ones to needy children in rural China, especially orphans. My entrepreneurial experience and growth are my most important accomplishment. It began as a passion but success followed, and it has shaped my academic and professional goals.

Winning a Lottery Essay Example | Topics and Well Written Essays - 750 words

Winning a Lottery - Essay Example The article's headline says, "Artist Wins Million." Included a picture of your surrounded by your family and friends. Everyone in the picture was smiling. But, the reality is different. With the help of this letter, I want to tell you some negative effects of sudden wealth. But my message is very clear that sudden wealth can bring nothing but unhappiness. It may directly effect on your personality, relationships, and lifestyle.Winning a lottery will create a sense of isolationism and you will be separated from friends and family. This could happen if the winner like you relocated into a new setting; therefore, it will disconnect you from your friends and family. As, what, I have recently experienced in my life. You could furthermore appeal new family and associates who could be characterized as being 'false' as their concerns are in the cash and not in your friendship. For example, there have been normal situations of distant or estranged relations abruptly and unexpectantly seeming out of the azure when hearing of a family member's latest fortunes. Eventually the one-by-one may not be adept to differentiate their authentic associates from the 'false' ones. They may then isolate themselves from all of them or just accept the realization that some of their associates are only actually involved in what the victor can do for them and not the victor themselves. Drastic change is abnormal and thus the one-by-one may not be adept ... There may furthermore be too much force on the individual. There are family constituents, associates as well as economic advisors, all of who have inconsistent and vying interests. This can lead to stress and tension as well as a lesson dilemma for the one-by-one as a outcome of them having to conclude between who they should hear to and take recommendations from. This could finally manifest itself into a pattern of guilt and hostility in the direction of these persons and loved ones. For this cause, the lottery can conceive an painful position for you and you may not have had to make such significant conclusions and choices. This could conceive an unhealthy and dejected state of brain for you that could finally lead to contradictory tendency. However, I would like to state that it is not triumphant the lottery that directs to persons committing suicide, but diverse socio-economic components and variables that are the genuine determinants of suicide. For example, if or not the one-by-one was struck as a progeny or if he/she came from a lone parent family are significant components that should be taken into account as they play a key function in forming a person's mind. The one-by-one could furthermore have been psychologically unstable in the first place. Therefore suicide can not be verified to be exactly associated to triumphant the lottery as the person's psychological state of brain before triumphant is a key determinant. Conclusion All in all, lottery winning will create troubles in your coming life. And you could be more irresponsible and unnecessary with your money than you must be. In the long run, the amount that you have won could be enormously

Homicide Term Paper Example | Topics and Well Written Essays - 1500 words

Homicide - Term Paper Example The discussion that follows will majorly deal with social learning theory, minds designed for murder theory, thrill murder theory and sociological theories including social-demographic theory, subculture violence theory and ‘victomology’. The Social learning theory In his famous publication Professor Bandura,1 has argued that human beings are not born with pre-determined repertoires and predispositions of aggressive behavior. As a matter of fact, most aggressive incidents viz fighting with switchblade knives, martialling with opponents, involvement in military activities, or taking part in vengeful ridicule suffices sophisticated skills that inevitably call for extensive social learning. Ultimately, unlike other basic forms of physical engagement requiring least guidance, victims of this theory, as Bandura observes must be learn them in a way or the other. Further, a progressive argument under this theory has indicated that instead of concentrating much on juvenile aggre ssion as a reason for homicide, a comprehensive analysis must be drafted to entail even the class of individuals who get to be legally trained or professionally acquire skills and knowledge especially those who belong to the category of people whose owe a national duty by providing military service. That being the position, it is therefore difficult to argue that any other skill acquired through social learning is always inclined towards the commitment of a homicide. This is because not the killings done by this class of people are majorly within the ambits permissible by the law. Such circumstances include killings in the course defense on national security, during wars and defense of citizenry property. As such this could be cited as a possible weakness under this theory. Further, this theory presupposes that behavior is reinforced by rewards and punishment and also by observing the behavior of others. Bandura in 1973 argued that people learn particularly from visual images as the just the same way the things happen. Aggressive behavior and violent individual aired through media viz TV can provide a model particularly for young people who try to emulate them. Philip and Hensley in 1984 argued that the number of homicide in the USA significantly increased after a big boxing context which had been viewed through TV. In 1993 two 10 year old boys murdered James Burgler after watching a violent match. Minds designed for murder theory In his famous publication Dr David Buss,2 under the theory of evolutionary psychology has argued that at one point in everyone’s life, there has been a strong and shocking urge to kill. His further pose that murder is our blood and specifically says that homicide is not uncommon pathology or the product of social thrust of culture, destitution or poor parenting but it is an evolutionary adaption that all human beings subject. He further observed that in the appropriate instances all human beings kill, this is by the reason tha t their ancestral fathers also did kill to procure greater chances of reproductive success.3 Ultimately, this is to date inherent in every human being. The component of Buss’ homicidal fantasy also works to suppress the idea that indeed at one moment every human being has killed either physical or by strip of mental fantasy (Buss, 2008). Drug related murder This theory suggests that Neal and Brendan were killed because of some kind of connection to illicit drugs. The theory arises because they

Personal exercise plan swimming Essay Example for Free

Personal exercise plan swimming Essay What I enjoy doing: I enjoy swimming, playing squash, jogging, aerobics and power walking. What activities I already take part in: I play squash two or three times a week, and got to the gym, and in the spring I cycle with my friends. I also have bleep test/ fitness test once every two weeks. By improving my muscle strength and endurance it will mean that I am able to train for longer. Cardiovascular fitness is the ability of your heart to deliver oxygen to your muscles over a long period of time. This will build up my heart muscle and allow me to train for longer and cope with the pace of a longer game. By improving my agility it will my ability to perform a series of explosive power movements in a rapid succession in opposing directions. By improving my speed I will be able to get across the court in less time so my opponent has less time to react. Testing my Fitness Level I am going to use specific tests, which are associated with my sport. I will test how fit I am at the beginning of the six week session. I will test my cardiovascular endurance and my muscular endurance. I will use my aerobic system, anaerobic system and my power. All the tests I decide to do at the beginning of the six weeks, I will repeat again at the end of it so I can see how much my fitness level has improved by. Swimming (set 1) is a continuous training session. This program is mainly going to contain aerobic training with some focus on anaerobic training, to help improve sprint starts and finishes in the water, and my overall speed. Swimming (set 2) will include several types of ketchup to improve my technique. In the program I must ensure that I have enough rest periods to prevent build up of lactic acid or injury Each week is going to include one circuit session and a two swimming sessions. The exercises of the circuit will be performed in the same order that they are written down. This way, after working each muscle group it is then rested by working another group. The number of repetitions, not how long it takes to carry out one activity, will perform my circuit. An example of a circuit session would look like this: At the beginning I will complete a small warm up, jogging 15m, and then stretching from the neck working downwards. Station 1: arms raises using dumb bells (3kg). I will repeat this 15 times on each arm, it will strengthen the muscles in my arms making them more powerful, and making me swim faster. Increase by: 5 arm raises each time. Station 2: V sits. 16 times, strengthening my stomach muscles. Increase by: 3 more v-sits each time. Station 3: cycles with ankle weights, and dumb bells in hands. I will do 20 cycles. This will work my quads, abs, arms and hamstring muscles, making them stronger. Increase by: 4 cycles each time. Station 4: running on a crash mat, 50 steps, this will strengthen my quads and my cardiovascular system. Increase by: 5 steps each time. Station 5: the plank. Hold it for 40 seconds, rest for 40 seconds, and then repeat it three times. This will strengthen my stomach muscles. Increase by: repeat it an extra time each time. Station 6: arm circles, 60 times. Will strengthen arm muscles, making my pulls in my strokes stronger, making me go faster. Increased by: 4 arm circles each time. Station 7: lunges with weights (3kg), 20 lunges. Strengthen my legs, enabling my kicks to be more powerful. Increase by: 2 lunges each time. Station 8: medicine ball lifts with arms, 15 times. Strengthen my arm muscles. Increase by: 2 lifts each time. Station 9: skipping: 50 skips, improve my cardiovascular system. Increase by: 5 skips each time. Station 10: step ups, 50 times strengthening the muscles in my legs. Increase by: 3 step ups each time. Station 11: running 15m 6times, strengthening my cardiovascular system Increase by: 1 15m run each time. At the end of my circuit training session, I will stretch all of my muscles to prevent the build up of laic acid. When I do my circuit training sessions I will increase the amount of reps I carry out, the number that I increase them by is underlined at the bottom of each section. I need to increase the number of reps so that my body does not adjust to the exercise I am doing, and it keeps improving, and so my muscles become stronger.

Synthesis And Characterization Of Strontium Ferrite Environmental Sciences Essay

Synthesis And Characterization Of Strontium Ferrite Environmental Sciences Essay Strontium ferrite is a ferromagnetic material and reported as having hexagonal magnetoplumbite type (M-type) structure. It is the most widely used permanent magnets throughout the world, which account for about 90wt% of the annual production of permanent magnets. In this study, the strontium ferrite is synthesized using sol-gel methods and the magnetic properties were analyzed. Chapter 1 gave introduction about the structure of M-type hexagonal strontium ferrite. Besides, some general magnetic properties will be discussed. Commercial applications of strontium ferrite would be discussed as well. Chapter 2 is all about the experimental details, including the synthetic techniques used for strontium ferrite, description of instrument used and procedures carried out. Chapter 3 concentrated on the results on magnetic susceptibility of hexagonal strontium ferrite. Comparison between strontium ferrite and cation-substituted strontium ferrite was made. Chapter 4 concluded the whole investigation of this study. Suggestions for future studies were also discussed. Better understanding of the properties and practical applications of strontium ferrite can be achieved through this study. ABSTRACT The properties of magnetoplumbite type (M-type) hexagonal strontium ferrite has been investigated. The attempt of substitution of cobalt(II) oxide and titanium(IV) oxide in order to produce a quaternary system of the type SrO-Fe2O3-XO where X represents the dopant cation was made. The synthesis is based on sol-gel method where ethylene glycol is the gel precursor. This technique was employed because it was found to be able to produce nanoparticles of cation substituted strontium ferrite. Moreover, sol-gel method can produce high yields of strontium ferrite particles. Overall, the magnetic properties were observed to be change after the cation substitution. Co(II)-Ti(IV) substitution in SrFe12O19 with different ratios were made in this study to investigate the effect of cation substitution in magnetic properties of strontium ferrite. Co(II)-Ti(IV) substitution in strontium ferrite with mole ratio of 0.4 showed the best magnetic properties that we desired for. The mass susceptibility where X = 0.4 was found to be increase sharply compared to the unsubstituted one. Except the cobalt titanium substitution with mole ratio of 0.4, other cation substitution ratios showed decrease in mass susceptibility which is not desirable. Therefore the cobalt-titanium substitution for SrCoxTixFe12-2xO19 with X = 0.4 is the best to improve magnetic properties of strontium ferrite for various commercial applications. REVIEW Strontium ferrite has been a subject of continuous interest and intensive study for several decades due to the fact that this compound has been the the most widely used permanent magnets, which account for about 90wt% of the annual production of permanent magnets since shortly after its discovery in the 1950s. Strontium hexaferrite, SrFe12O19, is a ferrimagnet and is also known as ceramic permanent magnet. When compared with alnico-magnets, strontium ferrite has high coercivity, moderate remenance, corrosion resistance and excellent chemical stability [5]. Iron(III) oxide (Fe2O3) is the principal components in SrFe12O19 which gives rise to its magnetic properties. Within the five different crystallographic sites of strontium ferrite, the iron ions are coupled antiferromagnetically. Due to its high magnetocrystalline anisotropy field in its structure, SrFe12O19 exhibits high saturation magnetization and high coercivity [1]. The high magnetic permeability in strontium ferrite enables i t to store strong magnetic fields, which is stronger than iron. Strontium ferrite is often produced as nanoscale size powder, which can be sintered into solid cores. Strontium ferrite has been used for several important industrial applications, such as permanent magnets, microwave devices and high density perpendicular recording media, with proper doping in order to improve properties of strontium ferrite [1]. SrFe12O19 has also been investigated as a medium for magnetic recording and magneto-optical recording and for long (millimetre)-wave devices [2]. Efforts have made to the development of novel synthetic methods which facilitate the production of fine hexagonal ferrite particles and to possible ways of reducing their high intrinsic magnetocrystalline anisotropy. The objective in this study was to attempt the synthesis of cation substituted M-type hexagonal ferrite SrCoxTixFe12-2xO19 using the sol-gel method. The sol-gel method has been used widely to produce fine particles of a variety of oxides. The effect of doping strontium ferrite with cobalt (II) and titanium (IV) oxides to produce quaternary systems of SrO-Fe2O3-XO, where X represents the dopant cation would be tested. The fine particles of cation substituted ferrite produced by using sol-gel technique is desirable because the grain size of the materials used in magnetic recording is the main factor determining the level of background noise at low density. Magnetic properties of strontium ferrite would be focus in this study. Magnetic susceptibility balance would be used to determine the mass susceptibility for both strontium ferrite and cation-substituted strontium ferrite produced using the sol-gel method. The mass susceptibilities of the samples were compared to determine the optimum amount of cation needed to dope to ferrite to give the best magnetic behaviour. CRYSTAL STRUCTURE OF M-TYPE HEXAGONAL SrFe12O19 According to crystalline structure, hexaferrite can be classified into four types, these include M, W, Y and Z types hexaferrites which correspond to (SrO + MeO):Fe2O3 ratios of 1:6, 3:8, 4:6 and 5:12 respectively. SrFe12O19 is classified as M-type hexaferrite. The hexagonal SrFe12O19 was first prepared by Adelsk ¨old in 1938 [2]. He also confirmed that the crystal structure of this compound to be iso-structural with the naturally occurring ferrite mineral magnetoplumbite, and therefore it has the M-type structure. Later structural refinements for strontium hexaferrite have confirmed his determination [2]. Strontium ferrite is classified as hexagonal ferrite. It is denoted as having the space group P63/mmc. According to the research made by Kimura et al, the lattice parameters measured are found to be: a = 0.588 36nm and c = 2.303 76nm at room temperature [2]. As shown for M-type hexaferrite BaFe12O19 in Fig. 1.1, the crystalline structures of different types of hexaferrites are remarkably complex. The unit cell contains ten oxygen layers. A unit cell is sequentially constructed for four blocks, they are S (spinel), R (hexagonal), S* and R*. The S and R blocks have equivalent atomic arrangements and are rotated around the c-axis at 180 ° with respect to S* and R* blocks. R or R* block consists of three O2à ¢Ã‹â€ Ã¢â‚¬â„¢Ã‚  layers while S or S* block contains two O2à ¢Ã‹â€ Ã¢â‚¬â„¢Ã‚  layers; with one oxygen site in the middle layer substituted by a Ba2+  ion [16]. The structure of strontium ferrite is similar to that of barium ferrite, by just substituting the barium ion with strontium ion. Fig.  1.1:  Structure of barium hexaferrite Occasionally, a unit cell is comprises of two formula units. The unit cell consists of 64 ions per hexagonal unit cell, which are 2 strontium ions, 38 oxygen ions and 24 ferric ions. The structure of magnetoplumbite are made of a layer of hexagonal close packed arrangement of oxygen and strontium ions, which is sandwiched between two spinal blocks containing a cubic close-packed arrangement of oxygen atoms with iron atoms. The iron atoms are positioned at five interstitial crystallographically different cation sites of the close-packed layers, namely 4f1 (tetrahedral site, A sites), 12k, 4f2, 2a (octahedral sites, B sites) and 2b (trigonal bipyramidal site) [15]. The tetrahedral iron oxide is FeO4, octahedral iron oxide consists of six oxygen ions, which is FeO6, and the formula for trigonal bipyramidal iron oxide is FeO5. A schematic M-type structural representation and the five Fe3+ sites are shown in Fig. 1.2 by Collomb et al. [15]. Figure 1.2: The crystal structure sketch map of the hexagonal M-type phase and the five Fe sites with their surroundings are displayed. The 2b sites only occur in the same layer with strontium ion. 12k site is the octahedral site of S and R blocks. There are two tetrahedral (4f1) sites and one octahedral (2a) site in centre of S block. The two octahedral (4f2) sites are found in the R block, adjacent to the strontium-containing layer. The M-type structure of strontium ferrite gives rise to its magnetic properties. Cation substitution to strontium ferrite may give chances whereby altering the structure and thus influence the magnetic properties. MAGNETIC PROPERTIES OF M-TYPE HEXAGONAL SrFe12O19 Strontium hexaferrite is a ferrimagnetic material. Since the free electrons in SrFe12O19 are in close proximity and remain aligned even the external magnetic field have been removed, it is able to retain a permanent magnetic field and is recognized as ferrimagnetic material. In 1950s Gorter predicted that the iron ions at the trigonal bipyramidal (2b) and octahedral (2a, 12k) sites have their spin orientation antiparallel to that of the iron ions at the 4f sites [2]. The antiparallel 4f1 and 4f2 and parallel 2a, 12k and 2b sublattices form the ferrimagnetic structure. The magnetic ordering corresponding to the magnetoplumbite structure of hexagonal strontium ferrite is well illustrated in Fig. 1.3. In S block, the majority ÃŽÂ ±-sublattice consists of four octahedral ions and the minority ÃŽÂ ²-sublattice contains two tetrahedral ions whereas R block contributes three octahedral ions and one trigonal ion to the majority sublattice and two octahedral ions to the minority sublattice. Figure 1.3: The schematic structure (left) of the SrFe12O19 with Gorters magnetic ordering (middle) along the c-axis. The large open circles are oxygen ions, the large broken circles are Sr ions; small circles with a cross inside represent Fe ions at 12k, small circles containing a filled circle inside represent Fe ions at 4f2, small unfilled circles represent Fe ions at 4f1, filled small circles represent Fe ions at 2a and small circles with a unfilled circle inside represent Fe ions at 2b. The magnetic structure suggested by Gorter is shown on the right, where the arrows represent the direction of spin polarization. From Fig. 1.3, we can summarizes the sites of Fe(III) ions corresponding to the spin direction, as in Table 1.1. Site Coordination Occupancy Direction of spin polarization 12k Octahedral 12 Up 2a Octahedral 2 Up 2b Trigonal Bypiramidal 2 Up 4f1 Tetrahedral 4 Down 4f2 Octahedral 4 Down Table 1.1: Fe(III) ion sites in M-type hexagonal ferrite Hysteresis Loop The magnetic properties of strontium ferrite can be examined through hysteresis loops. Hysteresis loop can be measured using instruments such as Vibrating Sample Magnetometer (VSM) and SQUID Magnetometry Measurements. When a magnetic material is placed in a magnetic field, the flux density (B) would lags behind the magnetizing force (H) that causes it, and this form hysteresis loop. From a hysteresis loop, we can identify the magnetic properties of the material, they are saturation magnetization, remanence or also known as remnant magnetization, and coercivity. A typical hysteresis loop is well illustrated in Fig. 1.4. Figure 1.4: Typical hysteresis loop (B-H curve) Initially, there is no applied magnetic field and it is known as unmagnetized state. After magnetic field is applied, it causes alignment. Until maximum magnetizing force applied, maximum flux density achieved at the same time and this phenomenon is known as saturation magnetization. At this point, the maximum number of spin has mobilized. Saturation magnetization is defined as the maximum possible magnetisation of a material. It is also a measure of strongest magnetic field a magnet can produce. The unit of saturation magnetization is in amperes per meter. Strontium ferrite is having high saturation magnetization at which it can store high amount of magnetizing force. As the magnetizing force being slowly removed, the alignment stays at the point where H = 0, this is known as remnant magnetization. Remnant magnetization is the magnetization left in a permanent magnet after an external magnetic field is removed. When a magnet is magnetized, it has remanence. It is usually measured in unit Tesla. Strong permanent magnet such as strontium ferrite has high remnant magnetization which means the high amount of magnetic force remains in it even after the magnetizing force is removed. As form Fig. 1.4, negative magnetic field is applied to demagnetize the permanent magnet. When the flux density (B) = 0, there is no magnetizing force remain in the magnet and the negative H needed to demagnetize the magnet is known as coercivity. Negative H is the magnetic field applied in opposite direction. Coercivity is measured in unit amperes per meter. Due to its high uniaxial magnetocrystalline anisotropy with an easy axis of magnetization along the hexagonal c-axis in the structure, SrFe12O19 has high coercivity. Anisotropy is directional or orientational effects in crystal structure of materials which can provide better magnetic performance along certain preferred axis. Therefore, we need to apply high negative magnetizing force to demagnetize strontium ferrite. Attempts have to be made to lower down the coercivity of strontium ferrite for usage. Units in Magnetism The units used in magnetism can be divided mainly into two categories, SI system and c.g.s system. The conversion table shown in Table 1.2 is to clarify the magnetism formulas in both SI and c.g.s systems and the conversion factors between them. Quantity Symbol SI Unit SI Equation c.g.s Unit c.g.s Equation Conversion Factor Magnetic Induction B tesla (T) B= µo(H+M) gauss (G) B = H+4à Ã¢â€š ¬M 1 T = 104  G Magnetic Field Strength H ampere/meter   (A/m) H = NÃÆ'-I/lc   ( lc magnetic   path, m) oersted (Oe) H = 0.4à Ã¢â€š ¬NÃÆ'-I/lc (lc magnetic   path, cm) 1 A/m =   4 à Ã¢â€š ¬ÃƒÆ'-10-3  Oe Magnetic Flux ÃŽÂ ¦ weber (Wb) ÃŽÂ ¦ = BÃÆ'-Ac (Ac area, m2  ) maxwell (M) ÃŽÂ ¦ = BÃÆ'-Ac (Ac area, cm2  ) 1 Wb = 108  M Magnetization M ampere/meter (A/m) M=m/V (m- total magnetic moment,   V- volume, m3  ) emu/cm3 M=m/V (m- total magnetic moment,   V- volume, cm3  ) 1 A/m = 10-3   emu / cm3 Magnetic Permeability of Vaccum  µo newton/ampere2  µo= 4à Ã¢â€š ¬ÃƒÆ'-10-7 1 4à Ã¢â€š ¬ÃƒÆ'-10-7 Inductance L henry L=ÃŽÂ ¼oÃŽÂ ¼N2Ac/lc (Ac- area, m2,   lc magnetic path, m) henry L=0.4à Ã¢â€š ¬ÃƒÅ½Ã‚ ¼N2Ac/lcÃÆ'-10-8 (Ac-area, cm2,   lc magnetic path, cm) 1 Emf (voltage) V volt V=-NÃÆ'-dÃŽÂ ¦/dt volt V=-10-8NÃÆ'-dÃŽÂ ¦/dt 1 Note: In the above equations, I = current (in amps), N = turns Table 1.2: Magnetism formulas in SI and c.g.s systems and their conversion factors for the magnetic units. 1.4 PHOTOLUMINESCENCE PROPERTIES OF SrFe12O19 According to the study of G. B. Teh et.al [3] on strontium ferrite, strontium ferrite was found to exhibit photoluminescence behavior. When a sample of strontium ferrite is excited at a certain wavelength, highest intensity of photoluminescence emission peaks was obtained. The ability of strontium ferrite to photoluminesce could be due to the oxygen vacancies in their lattice structure. The oxygen vacancies are assumed to cause the particles to exhibit photoluminescence behavior by acting as traps for mobile excitation. The oxygen vacancies have effective +2 charges, making them powerful electron capture centers. Valence electron would gain sufficient energy to jump from the valence band to the conduction band and leaving a gap known as hole during excitation. F-centers, which is the region where contain high amount of electrons would formed when the excited electrons being trapped in oxygen vacancies. These rich electron centers would lead to emission of luminescence when the holes and electrons recombine. 1.5 SYNTHESIS ROUTE OF SrFe12O19 The processing routes used for synthesis of strontium ferrite affect its properties much. Traditionally, this ferrite powder is synthesized by a mixed oxide ceramic method, which involves the solid-state reaction between SrCO3 and Fe2O3 at a high calcination temperature (about 1300 °C). However, uncontrolled particle morphology, larger particle size and agglomerates would be the biggest disadvantages of this technique. Besides, contamination would be introduced to the sample while subsequent milling of the calcined ferrite powder and this would affect the magnetic properties become less desirable. Therefore, the narrowed particle size distribution, refined particle size and minimal particle agglomeration has been the main concern during the synthesis of strontium ferrite. In order to improve the magnetic properties, numerous nonconventional soft synthetic routes have been carried out, including sol-gel synthesis [3], hydrothermal reaction [6], co-precipitation [7], citric acid method [8] and microemulsion processing [10]. In this study, the synthesis of strontium ferrite employed the sol-gel technique. It is a wet chemical route employing ethylene glycol as gel precursor. Sol-gel technique is the technique of using chemical substances which have high solubility in organic solvents to synthesize precursor compounds. The compounds are easily transformed into hydrated oxides on hydrolysis. The metal alkoxides formed can be removed easily using hydrolysis and thermal treatment and therefore results in hydrated oxides which are highly purify. Sol-gel method is used in this study because of its many advantages. Sol-gel technique is able to produce homogeneous nanosized crystallites. This method is tend to give shaped materials directly from a solution without passing through the powder processing and the fact that the annealing temperature is very low compared with other conventional technology. The crystalline size and properties of the ferrite produced are largely affected by calcinations temperature [3]. Sol gel method has the advantage that the crystal growth of particles is easier to control by varying the heat treatment [11]. It was reported that at 500ËÅ ¡C it produced only maghemite, ÃŽÂ ³-Fe2O3. A mixed product of magnetic ÃŽÂ ±-Fe2O3 and M-type SrFe12O19 were obtained at 600ËÅ ¡C. As the calcination temperature increase to 800ËÅ ¡C and above, there are only M-type SrFe12O19 phase was observed. Sol-gel synthesis is able to produce high yields of SrFe12O19 nanoparticles. It is also able to prod uce nanocrystallite of cation substituted SrFe12O19. Nanoparticle size of strontium ferrite is desirable and aimed to synthesize because nanoparticles tend to give better magnetic properties. Nanoparticles give few magnetic domains, probably single domain. Single domain tends to give higher magnetic induction because there are no oppose magnetic domain. Single domain aligns in one direction only. These properties are ideal for the making of permanent magnet. 1.6 CATION SUBSTITUTION IN SrFe12O19 In order to improve the magnetic properties of strontium ferrite, many studies have been carried out. One of them is cation substitution in strontium ferrite. Rare earth and other metal cations are used for substitution for strontium and iron respectively [5]. The pair doping of SrFe12O19 such as a La-Co pair to replace a Sr-Fe pair has been tested [14]. The doping, or known as cation substitution, is aim to improve the magnetic properties of strontium ferrite. Cation substitution results in structural changes in strontium ferrite. As the physical properties of ferrite change, the magnetic properties would be affected due to the fact that magnetic properties are determined by the arrangement of iron ions in crystal structure. In this study, Co-Ti pair will be doped to the strontium ferrite. Cobalt titanium substitution will produce a quaternary system of the type SrO-Fe2O3-AO where A represents the dopant cation.The cobalt titanium substitution gives rise to the new formula, SrCoxTix Fe12-2xO19 where X is the number of mole of cation substituted in. 1.7 Commercial Applications Strontium ferrite is widely used as permanent magnet because it has direction of easy magnetization and the hexagonal c-axis which are perpendicular to the plane of the plate. The properties that are desirable in using as permanent magnet include high saturation magnetization, high remnant magnetization, high coercivity, high Curie temperature and high magnetocrystalline anisotropy. Besides, SrFe12O19 is also commonly used in high-density data storage magnetic recording media. Nanoparticles of SrFe12O19 with single domain and low coercivity are crucial in used for magnetic recording media. M-type strontium ferrite nanoparticles have attracted much attention due to their good frequency characteristic, low noise, high output, in particular, excellent high frequency characteristic and wide dynamic frequency range [4]. There are two types of recording medium, namely particulates and thin films. Tape and floppy is categorized in particulate and hard drive is belongs to thin film. Information is stored by magnetizing material. The recording head can apply magnetic field (H) and align domains to magnetize the medium. It can also detect a change in the magnetization of the medium. Magnetic recording media prefers high saturation magnetization; make it to store as much information. High value of remnant magnetization is required in recording media to make sure that all m aterials stored in the hard disk still remained even the power supply (applied magnetic field) is switched off. Low coercivity is important in magnetic recording media. When the positive magnetic field is applied, this charging manages the medium to store data. On the other hand, negative magnetic field applied to retrieve back the data, this is called discharges. Therefore, less current is needed to retrieve the data in the low coercivity medium. As a result, less heat generated and this saves the electricity. In general, strontium ferrite has high value of uniaxial anisotropy field, high coercive force and high saturation magnetization. The high coercivity of strontium ferrite has to be lowered down and saturation magnetization has to be simultaneously increased if it is to be useful for magnetic recording purposes. It has been reported that the substitution of cations such as Co(II) for the ion Fe(III) in strontium ferrite has lowered the coercive force. Therefore, many studies were carried out to achieve better magnetic properties of strontium ferrite for commercial applications. CHAPTER 2: EXPERIMENTAL Sample Preparation Synthesis of M-type SrFe12O19 Synthesis of Cation Substituted SrFe12O19 Sample Characterization Magnetic Susceptibility Balance MK1 2.1 Sample Preparation 2.1.1 Synthesis of M-type SrFe12O19 The sol-gel technique was used to synthesize M-type SrFe12O19 whereby the ethylene glycol acts as gel precursor. The starting materials, strontium nitrate, Sr(NO3)2 and iron(III) nitrate-9-hydrates, Fe(NO3)3 ·9H2O were used due to their high solubility in ethylene glycol. Calculation below was made to determine the weight of materials needed to be used. Relative Molecular Mass of materials: Strontium nitrate, Sr(NO3)2 = 211.63 g/mol Iron(III) nitrate-9-hydrates, Fe(NO3)3 ·9H2O = 404 g/mol (Note: All answers have to be converted into 3 significant figures.) No. of mol of 1 g Sr(NO3)2 = Mass of Sr(NO3)2 RMM of Sr(NO3)2 = 1g 211.63g/mol = 4.725210-3 mol Sr : Fe = 1 : 12 No. of mol of Fe(NO3)3 ·9H2O needed = 4.725210-3 mol x 12 = 5.670210-2 mol Mass of Fe(NO3)3 ·9H2O needed = No. of mol of Fe(NO3)3 ·9H2O needed x RMM of Fe(NO3)3 ·9H2O = 5.670210-2 mol x 404g/mol = 22.9 g From the calculation, 1g of strontium nitrate and 22.9g of iron(III) nitrate-9-hydrates were needed in the synthesis and were weighted. Strontium nitrate would provided 1 mol of strontium ions and iron(III) nitrate-9-hydrates would provided 12 mol of iron ions in the synthesis of strontium ferrite, which matched the molecular formula of SrFe12O19. The strontium nitrate and iron(III) nitrate-9-hydrates were readily dissolved in ethylene glycol with slight heat applied due to their high solubility in it. The mixture was heated slightly and stirred with a magnetic bar until the mixture was fully dissolved. The resultant solution is in transparent reddish color. The magnetic stirring bar was removed. The mixture was heated to 100 °C and it would slowly transform into a gel form. The gel was dried with continuous heating at 100 °C for 3 hours. The dried gel was then transferred to a crucible to remove traces of organic precursor. A mixture of metal oxides in dispersed nanoclusters form was obtained. The dried gel was then annealed in a furnace at 800 °C for 3 days with extensive ground with a pestle in a mortar after annealed at interval of each day. 2.1.2 Synthesis of Cation Substituted SrFe12O19 Cation substituted strontium ferrite was synthesized by using cobalt(II) ions and titanium(IV) ions to substitute the iron ions in M-type hexagonal strontium ferrite. The substitution of Co(II) and Ti(IV) gives the compound a new molecular formula, which is SrCoxTixFe12-2xO19 where the x denoted different ratios. In the synthesis of cation substituted SrFe12O19, the ratios of cations used, x, is in between 0.2 to 6.0 (0.2 à ¢Ã¢â‚¬ °Ã‚ ¤ x à ¢Ã¢â‚¬ °Ã‚ ¤ 6.0), where x = 0.2, 0.4, 0.6, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0. The same method described in section 2.1.1 was used for the synthesis, by only adding two new starting materials, which are the cobalt(II) nitrate and titanium(IV) ethoxide to give the Co2+ and Ti4+ cations. Calculation as described below was made to calculate the weight of materials needed respectively. Relative Molecular Mass of materials: Strontium nitrate, Sr(NO3)2 = 211.63 g/mol Iron(III) nitrate-9-hydrates, Fe(NO3)3 ·9H2O = 404 g/mol Cobalt(II) nitrate, Co(NO3)2.6H2O = 291.04 g/mol Titanium(IV) ethoxide, Ti(CC2H5)4 = 228.11 g/mol (Note: All answers have to be converted into 3 significant figures.) Example used for the calculation: SrCo0.2Ti0.2Fe11.6O19, x= 0.2 No. of mol of 1 g Ti(CC2H5)4 = Mass of Ti(CC2H5)4 RMM of Ti(CC2H5)4 = 1g 228.11g/mol = 4.383810-3 mol 0.2 mol of Ti needed 1 mol of Sr. 4.383810-3 mol of Ti needed (4.383810-3 mol x 1) mol of Sr. 0.2 Therefore, 0.021919 mol of Sr is needed. Mass of Sr(NO3)2 needed = 0.021919mol x 211.63 g/mol = 4.64 g 0.2 mol of Ti needed 11.6 mol of Fe. 4.383810-3 mol of Ti needed (4.383810-3 mol x 11.6) mol of Sr. 0.2 Therefore, 0.25426 mol of Fe is needed. Mass of Fe(NO3)3 ·9H2O needed = 0.25426mol x 404g/mol = 103 g Mass of Co(NO3)2.6H2O needed = 4.383810-3 mol x 291.04g/mol = 1.28 g The calculation above were used to calculate the weight of starting materials needed for other cation ratios, x for 0.4, 0.6, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 respectively as well. The weight needed for each material was tabulated in Table 2.1. x Weight of materials needed (g) Sr(NO3)2 Fe(NO3)3 ·9H2O Co(NO3)2.6H2O 0.2 4.64 103 1.28 0.4 2.32 51.4 1.28 0.6 1.55 31.9 1.28 0.8 1.11 23.0 1.28 1.0 0.93 17.7 1.28 2.0 0.46 7.08 1.28 3.0 0.31 3.54 1.28 4.0 0.23 1.77 1.28 5.0 0.19 0.71 1.28 6.0 0.15 0.00 1.28 Table 2.1: Weight of materials needed for synthesis of Co(II)-Ti(IV) substituted strontium ferrite For the series of different substitution ratios (x), the corresponding strontium nitrate, iron(III) nitrate-9-hydrates, cobalt(II) nitrate and titanium(IV) ethoxide were weighed and dissolved in 100ml ethylene glycol. The oxides obtained after ignition were then annealed in a furnace at 800 °C for 3 days with extensive ground with a pestle in a mortar after annealed at interval of each day. The preparation for strontium ferrite and cation substituted strontium ferrite is shown in Fig. 2.1 in flow chart array. Figure 2.1: Schematic diagram of the procedure for synthesis of strontium ferrite and cobalt-titanium substituted SrFe12O19. Sample Characterization Magnetic Susceptibility Balance MK1 The magnetic properties of strontium ferrite and cobalt-titanium substituted strontium ferrite produced by the method described above were examined using the Magnetic Susceptibility Balance MARK 1 (MK1) by Sherwood Scientific Ltd, England. The magnetic susceptibility balance apparatus was shown in Fig. 2.2. Figure 2.2: Magnetic Susceptibility Balance MK1 by Sherwood Scientific Ltd, England. The basic design principle of Magnetic Susceptibility Balance MK1 was shown in Figure 2.3. Magnetic Susceptibility Balance determines the magnetic properties by placing two couple of moving magnets with the beam in between where the stationary sample is ready to be measured. Basically, the possible deflection in the beam and the movement being made of a particular sample either solid or liquid could be observed in a balanced system which possesses a magnetic field. Meanwhile, the coil within the instrument is conducted with current required in order to make compensation of the magnetic force produced by the sample. Either paramagnetic or diamagnetic could be resolved in a plus or minus relatively on display with the aid of the direction that the beam swifts. Figure 2.3: Basic design principle of Magnetic Susceptibility Balance MK1 by Sherwood Scientific Ltd, England. Magnetic susceptibility is defined as when the magnetising field is applied to the sample, how much is the ratio of the intensity of magnetism induced by the sample in response to the magnetising field which it is subject. In this experiment, mass susceptibility was the main concern. Mass susceptibility, xg, is defines by the mathematical formula below: à °Ã‚ Ã¢â‚¬ËœÃ‚ ¥g= à °Ã‚ Ã¢â‚¬ËœÃ‚ ¥v/d Where d = density of substance à °Ã‚ Ã¢â‚¬ËœÃ‚ ¥v is the volume susceptibility, calculated by using the formula: à °Ã‚ Ã¢â‚¬ËœÃ‚ ¥v = I/