If an object is placed in a magnetic field, then its “behavior” and the type of internal structural changes will depend on the material from which the object is made. All known substances can be divided into five main groups: paramagnets, ferromagnets and antiferromagnets, ferrimagnets and diamagnets. In accordance with this classification, the magnetic properties of a substance are distinguished. To understand what lies behind these terms, consider each group in more detail.
Substances exhibiting the properties of paramagnetism are characterized by magnetic permeability with a positive sign, moreover, regardless of the value of the intensity of the external magnetic field in which the object appears. The most famous representatives of this group are nitric oxide and gaseous oxygen, metals of alkaline earth and alkaline groups, as well as ferrous salts.
The high magnetic susceptibility of the positive sign (reaches 1 million) is inherent in ferromagnets. Being dependent on the intensity of the external field and temperature, the susceptibility varies widely. It is important to note that since the moments of elementary particles of different sublattices are equal in the structure, the total value of the moment is zero.
Both by name and by some properties, ferrimagnetic substances are close to them. They are united by a high dependence of the susceptibility on heating and the value of the field strength, but there are also differences. The magnetic moments of the atoms located in the sublattices are not equal to each other, therefore, unlike the previous group, the total moment is nonzero. The substance is inherent in spontaneous magnetization. The sublattice coupling is antiparallel. The most famous are ferrites. The magnetic properties of substances of this group are high, so they are often used in technology.
Of particular interest is the group of antiferromagnets. When these substances are cooled below a certain temperature boundary, atoms and their ions located in the structure of the crystal lattice naturally change their magnetic moments, acquiring antiparallel orientation. A completely different process takes place when a substance is heated — it exhibits magnetic properties characteristic of a group of paramagnets. Examples are carbonates, oxides, etc.
And finally, diamagnetics. The magnetic properties of the substances of this group do not depend on the field strength, and the value of the magnetic susceptibility is negative. If the substance has a covalent bond, then it is a “pure” diamagnet. Representatives - gold, copper, inert gases, etc.
The magnetic properties of the substance are widely used in modern technology. For example, turns of transformer windings are wound on soft magnetic materials. High magnetic permeability and magnetization to a state of saturation, even in a low-intensity field, mean a narrow hysteresis loop on the graph, as well as insignificant losses during magnetization reversal, which is in demand in electrical engineering. If the magnetic properties of a substance correspond to a soft magnetic material, then a product from it is characterized by a significant flux, limited only by saturation. In practice, this means the ability to reduce the dimensions of the magnetic circuit, thereby reducing the mass of the device. However, there is also a drawback in the advantages - the alternating field generates eddy currents in such material, which cause heating, so the conductor charge is a compromise solution.
Another type of material is magnetically hard, with a coercive force of at least 4000 amperes per meter. This means that magnetization reversal requires magnetic fields with high intensity, after which the material retains magnetic properties, turning into a permanent magnet.