Consider the main areas of application of ferromagnets, as well as the features of their classification. To begin with, ferromagnets are called solids that have uncontrolled magnetization at low temperatures. It changes under the influence of deformation, magnetic field, temperature fluctuations.
Properties of ferromagnets
The use of ferromagnets in technology is explained by their physical properties. They have magnetic permeability, which exceeds many times the permeability of vacuum. In this regard, all electrical devices that use magnetic fields to convert one type of energy into another have special elements made of a ferromagnetic material capable of conducting magnetic flux.
Features of ferromagnets
What are the distinguishing characteristics of ferromagnets? The properties and use of these substances is explained by the features of the internal structure. There is a direct relationship between the magnetic properties of matter and the elementary carriers of magnetism, which are played by electrons moving inside the atom.
While moving in circular orbits, they create elementary currents and magnetic dipoles with a magnetic moment. Its direction is determined by the rule of the gimlet. The magnetic moment of the body is the geometric sum of all parts. In addition to rotation in circular orbits, electrons also move around their own axes, creating spin moments. They perform an important function in the process of magnetization of ferromagnets.
The practical use of ferromagnets is associated with the formation in them of spontaneous magnetized regions in which the spin orientation is parallel. If the ferromagnet is not located in an external field, then the individual magnetic moments have different directions, their sum is zero and there is no magnetization property.
Distinctive features of ferromagnets
If paramagnets are associated with the properties of individual molecules or atoms of a substance, then the ferromagnetic properties can be explained by the specifics of the crystal structure. For example, in the vapor state, the iron atoms are slightly diamagnetic, and in the solid state this metal is a ferromagnet. As a result of laboratory studies, a relationship was found between temperature and ferromagnetic properties.
For example, in a Goisler alloy, similar in magnetic properties to iron, this metal is not. When the Curie point (a certain temperature value) is reached, the ferromagnetic properties disappear.
Among their distinguishing characteristics, one can distinguish not only a high value of magnetic permeability, but also the relationship between the field strength and magnetization.
The interaction of the magnetic moments of individual atoms of a ferromagnet contributes to the creation of powerful internal magnetic fields that line up parallel to each other. A powerful external field leads to a change in orientation, which leads to increased magnetic properties.
The nature of ferromagnets
Scientists have established the spin nature of ferromagnetism. When distributing electrons over the energy layers, the Pauli exclusion principle is taken into account. Its essence is that on each layer there can only be a certain number of them. The resulting values of the orbital and spin magnetic moments of all the electrons located on the completely filled shell are equal to zero.
Chemical elements having ferromagnetic properties (nickel, cobalt, iron) are transition elements of the periodic table. In their atoms, a violation of the electron filling of the shells occurs. First, they fall on the upper layer (s-orbital), and only after it is completely filled up do the electrons enter the shell located below (d-orbital).
The large-scale use of ferromagnets, the main of which is iron, is explained by a change in structure when it enters an external magnetic field.
Only those substances in whose atoms there are internal unfinished shells can possess similar properties. But even this condition is not enough to talk about ferromagnetic characteristics. For example, chromium, manganese, platinum also have unfinished shells inside atoms, but they are paramagnets. The occurrence of spontaneous magnetization is explained by a special quantum action, which is difficult to explain with the help of classical physics.
Subdivision
There is a conventional division of such materials into two types: hard and soft ferromagnets. The use of hard materials is associated with the manufacture of magnetic disks, tapes for storing information. Soft ferromagnets are indispensable when creating electromagnets, transformer cores. The differences between the two species are explained by the chemical structure of these substances.
Features of use
Let us consider in more detail some examples of the use of ferromagnets in various branches of modern technology. Soft magnetic materials are used in electrical engineering to create electric motors, transformers, generators. In addition, it is important to note the use of ferromagnets of this type in radio communications and low-current technology.
Hard views are needed to create permanent magnets. In the case of turning off the external field, ferromagnets retain their properties, since the orientation of elementary currents does not disappear.
It is this property that explains the use of ferromagnets. Briefly it can be said that such materials are the basis of modern technology.
Permanent magnets are needed when creating electrical measuring instruments, telephones, loudspeakers, magnetic compasses, sound recorders.
Ferrites
When considering the use of ferromagnets, special attention must be paid to ferrites. They are widespread in high-frequency radio engineering, because they combine the properties of semiconductors and ferromagnets. It is from ferrites that magnetic tapes and films, cores of inductors, disks are currently being made. They are iron oxides found in nature.
Interesting Facts
Of interest is the use of ferromagnets in electric machines, as well as in recording technology in a hard drive. Modern studies indicate that at certain temperatures, some ferromagnets can acquire paramagnetic characteristics. That is why these substances are considered poorly studied and are of particular interest to physicists.
The steel core is able to increase the magnetic field several times without changing the current strength.
The use of ferromagnets can significantly save electrical energy. That is why materials with ferromagnetic properties are used for the cores of generators, transformers, electric motors.
Magnetic hysteresis
This is the phenomenon of the dependence of the magnetic field strength and the magnetization vector on the external field. This property is manifested in ferromagnets, as well as in alloys made of iron, nickel, cobalt. A similar phenomenon is observed not only in the case of a change in the field in direction and magnitude, but also in the case of its rotation.
Permeability
Magnetic permeability is a physical quantity that shows the ratio of induction in a particular medium to that in a vacuum. If a substance creates its own magnetic field, it is considered magnetized. According to Ampere’s hypothesis, the value of the properties depends on the orbital motion of “free” electrons in the atom.
The hysteresis loop is a curve of the change in the size of the magnetization of a ferromagnet located in an external field on the change in the size of the induction. To completely demagnetize the body used, you need to change the direction of the external magnetic field.
At a certain magnitude of magnetic induction, which is called the coercive force, the magnetization of the sample takes on a zero value.
It is the shape of the hysteresis loop and the value of the coercive force that determine the ability of a substance to retain partial magnetization, explain the widespread use of ferromagnets. Briefly, the applications of hard ferromagnets with a wide hysteresis loop are described above. Tungsten, carbon, aluminum, chrome steels have a large coercive force, therefore, they create permanent magnets of various shapes based on them: strip, horseshoe-shaped.
Among soft materials having a small coercive force, we note iron ores, as well as alloys of iron with nickel.
The process of magnetization reversal of ferromagnets is associated with a change in the region of spontaneous magnetization. For this, work is used that is performed by an external field. The amount of heat generated in this case is proportional to the area of the hysteresis loop.
Conclusion
Currently, in all branches of technology, substances with ferromagnetic properties are actively used. In addition to significant savings in energy resources, the use of such substances can simplify processes.
For example, armed with powerful permanent magnets, you can greatly simplify the process of creating vehicles. Powerful electromagnets, currently used at domestic and foreign automobile plants, can fully automate the most labor-intensive technological processes, as well as significantly accelerate the assembly process of new vehicles.
In radio engineering, ferromagnets make it possible to obtain devices of the highest quality and accuracy.
Scientists have managed to create a one-step method for manufacturing magnetic nanoparticles, which are suitable for use in medicine and electronics.
As a result of numerous studies conducted in the best research laboratories, it was possible to establish the magnetic properties of cobalt and iron nanoparticles coated with a thin layer of gold. Their ability to transfer anti-cancer medicine or radionuclide atoms to the desired part of the human body, to increase the contrast of magnetic resonance images has already been confirmed.
In addition, such particles can be used to modernize magnetic memory devices, which will be a new step in creating innovative medical technology.
A team of Russian scientists managed to develop and test a method for the restoration of aqueous solutions of chlorides to obtain combined cobalt-iron nanoparticles suitable for creating materials with improved magnetic characteristics. All studies conducted by scientists are aimed at increasing the ferromagnetic properties of substances, increasing their percentage use in production.