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Classifications of Ferrite
Ferrite can be classified into spinel, garnet, and magnetoplumbite structure on the basis of crystal structure.
Spinel Ferrites
The chemical formula of spinel ferrites is MFe2O4 (M = Co2+, Mg2+, Mn2+, Zn2+, Cu2+, and Ni2+) which similarity with natural Magnesia-Alumina spinel MgAl2O4 and fall into the cubic system. Soft ferrites, rectangular loop ferrites, piezomagnetic ferrites, and partial gyromagnetic ferrites are all belong to spinel ferrites.
Garnet Ferrites
Garnet ferrite, also known as magnetic garnet, possesses similar crystal structure with natural garnet (Fe, Mn)3Al2(SiO4)3. Garnet ferrite is an excellent microwave material. Its chemical formula is M3Fe5O12 (M = Y3+, Sm3+, Eu3+, Gd3+, Dy3+, Ho3+) and fall into the cubic system. Yttrium-Iron garnet, also referred as YIG, is the outstanding representative of such material.
Magnetoplumbite Ferrites
Magetoplumbite ferrite fall into the hexagonal system and has similar crystal structure with natural magnetoplumbite Pb(Fe7.5Mn3.5Al0.5Ti0.5)O19. Magnetoplumbite (or simply ‘M’) type MFe12O19 (M = Ba2+, Sr2+, and Pb2+) ferrite is a permanent magnetic material with huge output. In addition, there are five more hexagonal ferrite which called W, X, Y, Z, and U type material.
Ferrite can be also divided into the soft ferrites, gyromagnetic ferrites, rectangular loop ferrites, piezomagnetic ferrites, and permanent ferrites depending on the characteristics and applications.
Soft Ferrites
Soft ferrite is a kind of ferrite material which easy to be magnetized or demagnetized and commonly applied under the weak magnetic field. Soft ferrites are primarily used as various inductors and widely utilized by communication, home appliances, office automation, and electronic countermeasure.
Gyromagnetic Ferrites
Gyromagnetic ferrite is also referenced as microwave ferrite. Gyromagnetic material generally constitutes various microwave devices with waveguide and transmission line.
Rectangular Loop Ferrites
Soft ferrite with a rectangular hysteresis loop is otherwise known as the rectangular loop ferrite. Frequently-used rectangular hysteresis material includes Lithium-Manganese and Magnesium-Manganese series product. Such materials are mainly applied in core memory of various electronic computers.
Piezomagnetic Ferrites
Piezomagnetic material refers in particular to the ferrite material which has magnetostriction via magnetic field direction. Piezomagnetic material is mainly utilized by ultrasonic, underwater acoustic, and magnetoacoustic devices.
Permanent Ferrites
Permanent ferrite is a ferrimagnetic metallic oxide which also referred as ferrite magnet, ceramic magnet, or hard ferrite. Permanent ferrites have preferable coercivity, corrosion resistance, and cost advantage in comparison with AlNiCo magnet, therefore, the presence of permanent ferrites was not only saving the strategic resource Cobalt and Nickel, but also carved out a new path for high frequency magnetic applications at that time. Permanent ferrites are commonly used in numerous areas in the past several decades and its market share is still very huge even application range of Neodymium magnet is more and more extensive.