1.1 high frequency , low heat resistance, high

1.1 INTRODUCTION TO FERRITE: Magnetic materials play an important role in electronics devices. It has many technological and electrical applications in the present civilization .

1Ferrites have relevant value in the class of ceramic oxides which exhibit magnetic and electrical properties .2Ferrites are ferromagnetic material which have double oxide of iron with other materials.(K).

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Ferrites have widely used in modern civilization .The main cause of widely used of ferrites in the magnetic field is the ability to the outfitter material with outstanding magnetic properties which compared to bulk system because of their construction. 1 The characteristics of ferrites depend on the chemical composition cation distribution and the formulation of preparation method. Ferrites are significant branch of ferromagnetic which are most important material both application and theoretical view of point. Ferrites have high resistivity which varies from 102 to 1010 ohm-cm which are 15 times higher than that of iron. Because of these magnificent properties of ferrites ,it make them more demandable for high frequency application .

(K) Ferrites have high frequency , low heat resistance, high corrosion resistor ,which make them more demandable for electromagnetic devices .The ferrites which behave as soft magnetic materials due to their exchange interaction among the cation of polyhedral sites. The rare earth cation have 4f orbital totally screened by 5s and 5p orbital these play an important role to explain electrical and magnetic properties of ferrites. The rare earth substituted ferrites have an important contribution in modern communication and electronic devices.3Nano-crystalline ferrites are most important because of their unique electric, dielectric, magnetic and optical properties which have a remarkable application both theoretical and technological sides.

In ferrites strong degrease in the saturation magnetization (Ms ) and of coercivity (Hc ) in comparison to the bulk modulus have been studied. Ferrites nanoparticles are widely used in electronics, bioprocessing magnetic resonance imaging Ferro fluids. Spinel soft ferrites are specially important because they are relatively inert and their properties can be tailored by chemical multiplication .

In recent years number of chemical and physical methods include mechanical milling, severe plastic deformation consolidation and inert gas condensation .4 Spinel ferrite have a significant application in electrical components such as memory devices and microwave devices and these ferrites have wide range frequency because of their high resistivity and loss behavior .5 Ferrites are used as high purity metal oxide which are prepared by ceramic technology .In these method the ferrites which are prepared are bulk material .In the modern nanotechnology, by using many different methods ferrites have been made Nano size particle.

(Chapter 7,5). 1.2: IMPORTANCE OF FERRITESFerrites have many important application in magnetic materials at higher frequency, lower price, greater heat resistance and higher corrosion resistance. These materials have many technological importance at variety of areas ,the use of ferrites have increased day by day .Because of their good magnetic properties and high electrical resistivity over a wide range frequency which start from a few hundred Hz to several GHz , polycrystalline ferrites have great importance in magnetic field .

Among the soft magnetic materials .They have high magnetic permeability and low magnetic losses so that spinel ferrites are used in many electronic and magnetic devices. 6 Ferrites have many importance in magnetic materials .These are-1. High resistivity 2. Wide frequency range (10kHzto50MHz) 3.

Low cost 4. Large selection material 5. Shape versatility 6. Economical assembly 7. Temperature and time stability 8.

High Q/small packageIn magnetic circuit ferrites are intended for both low level and power application because they have high frequency act of other circuit components continues to develop .They have advantageous arrangement of low cost ,high Q ,high stability and lowest volume so that these are finest core material choice for frequencies from 10KHz to %0MHz .In magnetic and mechanical considerations ferrites deal unmatched flexibility .7In recent years ,many consideration has been paid to Nano magnetic materials that response many magnetic properties .

Ferrites have many promising characteristics .The important properties of High quality factor such as brilliant magnetic and electrical enactment ,low sensitivity to difference in the ambient temperature ,good sensibility with time ,satisfactory performance over the vital frequency band ,large number of controllable parameters i.e, their electrical magnetic properties can be organized by changing the relative percentage of numerous can constituents of cautions and they are cost effective. 81.3: APPLICATIONS OF FERRITEFerrite materials technology is in an on new aged now, in which the design engineers control the properties to enormous amount, to uniform the particular device .In recent year technology depend a lot to ferrites industry .

Ferrites have great impact on ranging from the very ordinary radio sets to the complex and extensive hardware’s involved in computer .The first attraction of ferrites which is outstanding property is their very high electrical resistivity as compared to that of other metals .Eddy current losses are negligible at high frequency application ,in ferrites necessary materials telecommunication and in electronic industry where frequency range 103 to 1011 .Around 1950 ,new magnetic material was urgently need for telephone industry which was used as load coils of their long distance lines and magnetic in band pass filters .

For these necessity ferrite introduce new requirement .Another important use of ferrite is in resonance circuit .For inductors ferrite core was used .As it control and minimize the various loss factor ,ferrite core become very efficient inductor which have high initial permeability and reduced physical size .

Ferrite cores have high saturation induction and low hysteresis losses for these case core are used as power transformers . 8To control microwave transmission path ,frequency ,amplitude ,and phase microwave signals ,spinel ferrites are broadly used .To contribution in the production of ferrite ,perfect dielectric and magnetic property measurement at the operational frequency and temperature ranges are required for elevated improvement of theses metal. 9Magnetic materials have many possible application from information technology to biotechnology so that the structure of these materials are interesting field of study .

9Magnetic materials have many possible application from information technology to biotechnology so that the structure of these materials significant field of research .10Now a days for development of the fabrication of multilayer chip inductors MLFCI as surface mount devices for miniaturized electronic products such as cellular phones ,digital diaries ,video camera recorders ,floppy drives, etc are greatly used of Ni-Cu-Zn spinel ferrites substituted rare earth iron .11To manufacture multilayer chip inductors thin sheets made of ferrite or special ceramics are used on which coil patterns are printed with metal paste .A spiral shape electrode pattern is designed by organizing these sheet in multiple layers .The coil was formed by using multilayer technique which is in a three dimensional space without the need to wind wire on a core and its facilitates miniaturization and mass production .

At the time of flowing current through the coil magnetic flux is formed .The number of magnetic lines is known as inductance which is the intensity of the flux .The number of coil windings squared proportionally increased with the increased of inductance and proportionally to the cross section area.

For higher magnetic permeability ferrites are used as a core results in higher inductance. The concentration of magnetic field lines are affected by higher magnetic permeability of core. As Ni-Cu-Zn ferrites have lower sintering temperature rather than other ferrites, these are potential material for the MLCIs. Different types of ferrites have been used in audio and visual tools such as liquid crystal TV set, head phone stereos, computer and telecommunications devices such as personal wireless communication system and automobile telephones.12 ,13Ferrites have many important application. Those are given below 1-For modern electronic device such as cellular phones, video cameras, note book, hard temperatures and floppy drives ferrites are used.

2-Ferrites have oxides which can sintered at relatively low with a wide range composition so that these are used for manufacturing multilayer-type ships. 3-For low power and high flux transformers ferrites are used in television.4-Ferrites rod are used for producing small antennas which are used for radio receiver .

5-Ferrites made nonvolatile memories of computer .It collection information if power supply fails.6-Ferrites have been used for developing microwave devices such as circulators, insulators, switches.7-Because of their high frequency ferrites are used as transformer core and computer memories such as computer hard disk, floppy disks, credit cards, audio cassettes and recorder heads.8-For preparing low frequency ultrasonic waves ferries are used.9-Nickel alloys have high frequency for these reason these are used as high speed relays, wideband transformers and inductors.

These precise voltage and current transformers and inductive potentiometers.10-At low dielectric values ferrites are used as electromagnetic wave absorbers.1.4: CLASSIFICATION OF FERRITESAccording to magnetic behavior ferrite materials are classified into two categories- 1. Soft ferrites 2.

Hard ferritesSoft Ferrites: The ferrites which have low coercivity are called soft ferrites. These ferrites are combination of nickel, zinc, or manganese compounds. It is easy to magnetized and demagnetized soft ferrites. Because of their relatively low losses high frequency soft ferrites are widely used in core of switched-mode power supply (SMPS) and radio frequency (RF) transformers and inductors.Hard Ferrites: The ferrites which are permanent known as hard ferrites. Hard ferrites have high remanence after magnetization and these are combination of iron and barium or strontium oxides.

They have high magnetic permeability and conduct magnetic flux good in magnetically saturated state. It stores stronger magnetic field rather than iron so that it called ceramic magnet. These are used as magnet in radios. Hard ferrites have magnetic field strength near 30 to 160 KA turns per meter and magnetic field B is about 0.35. These ferrites are divided in M-, X-, W-, Y- and Z- kinds of ferrites and contain hexagonal structure.

7According to crystal structure ferrites are classified by four type- 1. Spinel Ferrites2. Garnet 3.

Ortho-ferrite and 4. Hexagonal ferrites 1) Spinel ferritesSpinel ferrites are also known as cubic ferrites. It is most famous ferrites because of their high value resistivity and low eddy current and for these properties spinel ferrites are ideal for microwave frequencies (Chapter 7). The chemical formula of spinel ferrites is MFe2O4. Here M means divalent metal ions. Spinel ferrites have two interstitial sites one is tetrahedral (A) and other is octahedral (B).

The properties of ferrites differ by adding different kind of cations at tetrahedral A site and octahedral B site. Here for get number of spinel ferrites M can be exchanged by other divalent ion metals. The divalent metal ion are Co2+, Zn2+, Fe2+, Mg2+, Ni2+, Cd2+,Cu2+.Spinel ferrites have eight formula per unit cell which is known as FCC unit cell.

Here the big anion create FCC lattice. According their distribution of cation on tetrahedral (A) and octahedral (B) sites spinel ferrites are classified into three different types. These are –a) Normal Spinel ferrites b) Inverse Spinel Ferritesc) Intermediate Spinel Ferritesa) Normal spinel ferritesThe spinel is normal when the octahedral B site has only one cation. In these case the trivalent cations are on octahedral B site on the other hand divalent cations are on tetrahedral (A) sites. Square brackets specify the ionic circulation of the octahedral B sites.

Normal spinel ferrites have been symbolized by the symbol (M2+)AMe3+BO4. Here M symbolized divalent ions and Me symbolized trivalent ions. ZnFe2O4 is a typical symbol of normal spinel ferrite.

b) Inverse Spinel FerritesIn spinel inverse ferrite partial of the trivalent ions are on the tetrahedral (A) sites and partial are on the octahedral B sites, the lasting cations are on arbitrarily distributed among the octahedral B sites. These spinel ferrites are symbolized by the formula (Me3+)AM2+Me3+BO4. Fe3O4 is the usual pattern of the spinel inverse ferrite.

14 c) Random spinel FerritesThe middle stage between normal and inverse ferrite with spinel ionic distribution known as random spinel ferrite. MgFe2O4 and MnFe2O4 are example of the random spinel ferrites.2) GarnetsGarnet ferrites are second type of ferrite having cubic structure which represented by the formula R33+Fe53+O12. Here R is the symbol of the rare earth element such as dysprosium (Dy3+), gadolium (Gd3+), samarium (Sm3+) etc. Fe3+ is replaced by trivalent metal ion such as Cr, Al etc 2. These metal ions are distributed over three different sites The metal ions are distributed over three types of sites.

The Me ions occupy the dodecahedral sites (called c sites), where they are surrounded by eight oxygen ions, the Fe3+ ions distributed over the tetrahedral and octahedral sites in the ratio 3:23) Ortho Ferrite 1 M. Kaiser, “Effect of rare earth elements on the structural, magnetic and electrical behavior of Ni-Zn-Cr nanoferrites,” J. Alloys Compd.

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