Magnetic Classification of Materials

Magnetic materials are defined as materials that are attracted to a magnet by a magnetic field. The magnetic substances are iron, nickel, and cobalt, which are distinguished by the fact that items formed of these materials are attracted to a magnet. Aside from that, magnetic materials have the ability to be magnetised, or to put it another way, magnetic materials have the ability to be transformed into magnets. 

Magnetic classification of material

Depending on their bulk magnetic susceptibility, all materials can be categorized according to their magnetic behavior, with the majority of them falling into one of five groups. In magnetism, the two most common types are diamagnetism and paramagnetism. These two types of magnetism account for the magnetic properties of most of the elements in the periodic table at room temperature.

These elements are commonly referred to as non-magnetic, whereas those that are commonly referred to as magnetic are really categorized as ferromagnetic, according to their magnetic properties. Antiferromagnetism is the only other type of magnetism that can be observed in pure elements when they are kept at room temperature. In addition, ferrimagnetic materials can be categorized as magnetic materials, despite the fact that this property is not observed in any pure element and can only be found in compounds, such as mixed oxides, which are known as ferrites, and where the term ferrimagnetism receives its name. When it comes to different types of materials, the value of magnetic susceptibility falls within a specific range.

Diamagnetism

A diamagnetic substance has no net magnetic moment when there is no applied field because the atoms have no net magnetic moment. While under the influence of an applied field (H), the spinning electrons process, and this motion, which is a sort of electric current, results in the production of magnetization (M) which is the polar opposite of the applied field. The diamagnetic effect is present in all materials; nevertheless, the diamagnetic effect is sometimes overshadowed by the larger paramagnetic or ferromagnetic terms. The value of susceptibility is unaffected by changes in ambient temperature.

Paramagnetism

Several theories of paramagnetism have been proposed, each of which is valid for a certain type of material. The Langevin model, which is valid for materials with non-interacting localized electrons, states that each atom has its own magnetic moment, which is randomly oriented as the result of thermal agitation, and that this is true for all materials. The application of magnetic field results in a modest alignment of these moments and, as a result, a low magnetization in the direction of the application of the magnetic field. Temperature increases cause thermal agitation to grow, which makes it more difficult to align the atomic magnetic moments, resulting in a drop in susceptibility as the temperature rises. This behavior is referred to as the Curie law, and it is illustrated in Eq1 below, where C is a material constant referred to as the Curie constant.

x=CT

Ferromagnetism

When atoms are organized in a lattice, the atomic magnetic moments can interact and align parallel to one another, which is the only way that ferromagnetism is feasible. A molecular field within the ferromagnetic material, as proposed by Weiss in 1907, is thought to be responsible for this result, which is explained by classical theory. This magnetic field is sufficient to magnetize the material to saturation levels without overheating it. Known as the Heisenberg model of ferromagnetism in quantum physics, it represents the parallel alignment of magnetic moments in terms of the exchange interaction between nearby moments between two magnetic moments.

To explain the presence of magnetic domains inside the material, Weiss hypothesized that these domains would be places where the atomic magnetic moments are aligned. The mobility of these domains affects how a material responds to a magnetic field, and as a result, the susceptibility is a function of the magnetic field applied to the material in question. Consequently, rather than in terms of susceptibility, ferromagnetic materials are typically compared in terms of saturation magnetization (magnetization when all domains are aligned).

Antiferromagnetism

Chromium is the only element in the periodic table that exhibits antiferromagnetism at room temperature, and it is also the most abundant. Despite the fact that antiferromagnetic materials are remarkably similar to ferromagnetic materials, the exchange contact between nearby atoms causes the anti-parallel alignment of the atomic magnetic moments in antiferromagnetic materials. So the magnetic field cancels out and the material looks to act similarly to a paramagnetic substance, which is what it is. These materials, like ferromagnetic materials, become paramagnetic when they reach a certain temperature, known as the Néel temperature, TN. (For example, Cr reaches TN=37oC.)

Ferrimagnetism

Ferrimagnetism can only be observed in compounds, which have more complex crystal structures than pure elements and hence exhibit greater magnetic repulsion. The exchange interactions that occur within these materials cause atoms to align in parallel in some crystal sites while aligning in anti-parallel in others. Similar to a ferromagnetic material, this material breaks down into magnetic domains, and the magnetic behavior is likewise fairly similar, however ferrimagnetic materials often have lower saturation magnetizations than ferromagnetic materials. For example, in barium ferrite (BaO.6Fe2O3), the unit cell contains 64 ions, of which the barium and oxygen ions have no magnetic moment, 16 Fe3+ ions have moments aligned parallel to the applied field and 8 Fe3+ ions have moments aligned antiparallel to the applied field, resulting in a net magnetization parallel to the applied field, but with a relatively low magnitude because only 1/8 of the ions contribute to the magnetization

What is non-magnetic material?  

Non-magnetic materials are materials that are not attracted to a magnet and are therefore referred to as such. All substances other than iron, nickel, and cobalt are classified as nonmagnetic substances; for example, plastic, rubber, water, and other nonmagnetic materials are classified as nonmagnetic materials. It is impossible to magnetize non-magnetic material.

Conclusion

All materials can be categorized according to their magnetic behavior. Most fall into one of five groups, the most common of which is diamagnetism. Other types of magnetism can only be observed in compounds, such as mixed oxides or ferrimagnetes. The value of magnetic susceptibility falls within a specific range. In quantum physics, atoms are organized in a lattice so that atomic magnetic moments can interact and align parallel to one another.

A molecular field within the material is thought to be responsible for this phenomenon. This magnetic field is sufficient to magnetize the material to saturation levels without overheating it. Ferrimagnetism can only be observed in compounds, which have more complex crystal structures than pure elements and hence exhibit greater magnetic repulsion. The exchange interactions that occur within these materials cause atoms to align in parallel in some crystal sites while aligning anti-parallel in others.