MnZn have higher permeability and saturation induction than NiZn. Manganese-zinc ferrite ( MnZn, with the formula Mn aZn (1-a)Fe 2O 4).

Because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies and loopstick antennas used in AM radios. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy ( hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. As a result, soft ferrites are also called transformer ferrites.They have a low coercivity. Soft ferrites are commonly used as transformers (to change the voltage from primary to secondary windings). They have magnetism (much like mild steel), but when the magnetic field is removed, the magnetism decreases. Various ferrite cores used to make small transformers and inductorsįerrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. In terms of their magnetic properties, the different ferrites are often classified as 'soft', 'semi-hard' or 'hard', which refers to their low or high magnetic coercivity, as follows. Some ferrites adopt hexagonal crystal structure, like barium and strontium ferrites BaFe 12O 19 (BaO:6Fe 2O 3) and SrFe 12O 19 (SrO:6Fe 2O 3). The magnetic material known as 'ZnFe' has the formula ZnFe 2O 4, with Fe 3+ occupying the octahedral sites and Zn 2+ occupy the tetrahedral sites, it is an example of normal structure spinel ferrite. It is also possible to have mixed structure spinel ferrites with formula O 4 where δ is the degree of inversion. Spinel ferrites usually adopt a crystal motif consisting of cubic close-packed (fcc) oxides (O 2−) with A cations occupying one eighth of the tetrahedral holes and B cations occupying half of the octahedral holes, i.e., A 2+įerrite crystals do not adopt the ordinary spinel structure, but rather the inverse spinel structure: One eighth of the tetrahedral holes are occupied by B cations, one fourth of the octahedral sites are occupied by A cations. Many ferrites adopt the spinel structure with the formula AB 2O 4, where A and B represent various metal cations, usually including iron (Fe). Like most of the other ceramics, ferrites are hard, brittle, and poor conductors of electricity. Composition, structure, and properties įerrites are usually ferrimagnetic ceramic compounds derived from iron oxides.

Yogoro Kato and Takeshi Takei of the Tokyo Institute of Technology synthesized the first ferrite compounds in 1930. They are used in the electronics industry to make efficient magnetic cores called ferrite cores for high-frequency inductors, transformers and antennas, and in various microwave components.įerrite compounds are extremely low cost, being made of mostly iron oxide, and have excellent corrosion resistance. Soft ferrites have low coercivity, so they easily change their magnetization and act as conductors of magnetic fields. They are used to make permanent magnets for applications such as refrigerator magnets, loudspeakers, and small electric motors. Hard ferrites have high coercivity, so are difficult to demagnetize.

Ferrites can be divided into two families based on their resistance to being demagnetized (magnetic coercivity). Unlike other ferromagnetic materials, most ferrites are not electrically conductive, making them useful in applications like magnetic cores for transformers to suppress eddy currents. They are ferrimagnetic, meaning they can be magnetized or attracted to a magnet. A ferrite is a ceramic material made by mixing and firing large proportions of iron(III) oxide ( Fe 2O 3, rust) blended with small proportions of one or more additional metallic elements, such as strontium, barium, manganese, nickel, and zinc.

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