Ferrimagnetic Material

In this lecture, we are going to learn about Ferrimagnetic Material, the properties of Ferrites, and the applications of ferrites. So let’s discuss each topic one by one in detail.

Table of Contents

In ferrimagnetic materials, magnetic dipoles are aligned in an antiparallel direction but the strength of dipole moment is higher in one direction to other directions, so as a result material possesses net magnetization.

The ferrimagnetic materials with low conductivity and high resistivity are known as ferrites.

Ferrites lose their property of ferrimagnetism above a critical temperature known as Curie temperature and start behaving like paramagnetic material.

Below Cuire temperature they exhibit similar properties as that of ferromagnetic materials (property of hysteresis).

Ferrites have high resistivity so they are preferred for high-frequency applications (up to microwave frequencies).

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Properties of Ferrites

Ferrites are a type of ferrimagnetic material that is composed of iron oxide (Fe3O4) and one or more other metallic elements, such as zinc or manganese. They have a number of unique properties that make them useful in a variety of applications. Some key properties of ferrites include:

High electrical resistivity: Ferrites have a high electrical resistivity, which makes them useful in electrical insulation and electromagnetic shielding applications.

High magnetic permeability: Ferrites have a high magnetic permeability, which means they can easily be magnetized and demagnetized. This makes them useful in the production of magnetic cores for electrical transformers and inductors.

High magnetic coercivity: Ferrites have a high magnetic coercivity, meaning they are resistant to losing their magnetization when subjected to an external magnetic field. This makes them useful in the production of permanent magnets and magnetic storage media.

High melting point: Ferrites have a high melting point, which makes them useful in high-temperature applications.

Good chemical stability: Ferrites are chemically stable and resistant to corrosion, which makes them useful in a variety of applications.

Example:

(i) Simple ferrites having formula MeO.Fe2O3 where Me corresponds to divalent metals like Fe, Co, Mn, Zn, Cd, etc.

MnO.Fe2O3 $\rightarrow$

(ii) Garnet/ Rare earth ferrites (formula 3 M2O3. 5 Fe2O3)

Where M = rare earth garnet

(a) YIG -> Yttrium iron garnet

(b) YIAlg -> Yttrium iron aluminium garnet

Advantages of Ferrimagnetic Material

Ferrimagnetic materials have a number of advantages that make them useful in a variety of applications. Some key advantages of ferrimagnetic materials include:

Strong magnetization: Ferrimagnetic materials have a strong tendency to maintain their magnetization, making them useful in the production of permanent magnets.

High magnetic coercivity: Hard ferrimagnetic materials have a high magnetic coercivity, meaning they are resistant to losing their magnetization when subjected to an external magnetic field. This makes them useful in the production of magnetic storage media, which needs to maintain its magnetization over long periods of time.

Easy magnetization and demagnetization: Soft ferrimagnetic materials are easily magnetized and demagnetized, making them useful in applications where the magnetization needs to be easily changed, such as in magnetic cores for electrical transformers and inductors.

Versatility: Ferrimagnetic materials can be used in a wide variety of applications, including permanent magnets, magnetic storage media, magnetic cores, sensors, and RFID tags.

Durability: Ferrimagnetic materials are generally resistant to corrosion and have a long lifespan, making them useful in applications where durability is important.

Applications of Ferrites

The applications of ferrites can be put broadly into four broad categories (primary ceramic ferrites)

(i) Soft ferrites: These ferrites have high permeability low coercive force, narrow hysteresis loop, low eddy current losses, and high resistivity. These ferrites are used for making core electromagnets and high-frequency transformers.

(ii) Hard Ferrites: These ferrites have a high value of coercive force, high residual magnetism, and a broad hysteresis loop. These ferrites are used for making permanent magnets required in high-frequency applications.

(iii) Rectangular loop Ferrites: These ferrites have an almost rectangular shape of the hysteresis curve. Due to this feature, they are used in making magnetic memories to store digital data.

(iv) Microwave Ferrites: The ferrites are used especially for microwave applications and are known as microwave ferrites. With these frequencies, the electromagnetic wave interacts with the dipole and results in faraday rotation.

(v) Permanent magnets: Hard ferrimagnetic materials are often used in the production of permanent magnets, which are used in a variety of applications including generators, motors, and loudspeakers.

(vi) Magnetic storage media: Hard ferrimagnetic materials are also used in producing magnetic storage media, such as hard disk drives and magnetic tape, which are used to store data digitally.

(Vii) Magnetic cores: Soft ferrimagnetic materials, such as iron, cobalt, and nickel, are often used in the production of magnetic cores for electrical transformers and inductors. These cores help to concentrate the magnetic field in these devices and enhance their performance.

(viii) Sensors: Ferrimagnetic materials are often used in sensors that measure magnetic fields, such as magnetoresistive sensors and giant magnetoresistive sensors. These sensors are used in a wide range of applications, including navigation, medical imaging, and geophysical exploration.

(iX) RFID tags: Radio-frequency identification (RFID) tags use ferrimagnetic materials to store and transmit data wirelessly. These tags are used in a variety of applications, including inventory management, asset tracking, and supply chain management.

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