Let's consider the main areas of application of ferromagnets, as well as the features of their classification. Let's start with the fact that 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 a magnetic permeability that is many times greater than that of a 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 a magnetic flux.
Features of ferromagnets
What are the distinguishing characteristics of ferromagnets? The properties and use of these substances are explained by the peculiarities of the internal structure. There is a direct relationship between the magnetic properties of matter and the elementary carriers of magnetism, which are electrons moving inside the atom.
While moving in circular orbits, they create elementary currents and magneticdipoles that have a magnetic moment. Its direction is determined by the gimlet rule. The magnetic moment of a body is the geometric sum of all parts. In addition to rotating 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.
Practical application of ferromagnets is associated with the formation in them of spontaneous magnetized regions with parallel orientation of spin moments. 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 ferromagnetic properties can be explained by the specifics of the crystal structure. For example, in the vapor state, iron atoms are slightly diamagnetic, while in the solid state this metal is a ferromagnet. As a result of laboratory studies, the relationship between temperature and ferromagnetic properties was revealed.
For example, in the Goisler alloy, similar in magnetic properties to iron, this metal is not present. When the Curie point (a certain temperature value) is reached, the ferromagnetic properties disappear.
Among their distinctive characteristics, one can single out not only the high value of magnetic permeability, but also the relationship between the field strength andmagnetization.
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 strong external field leads to a change in orientation, which leads to an increase in magnetic properties.
Nature of ferromagnets
Scientists have established the spin nature of ferromagnetism. When distributing electrons over energy layers, the Pauli exclusion principle is taken into account. Its essence is that only a certain number of them can be on each layer. The resulting values of the orbital and spin magnetic moments of all electrons located on a completely filled shell are equal to zero.
Chemical elements with ferromagnetic properties (nickel, cob alt, iron) are transitional elements of the periodic table. In their atoms, there is a violation of the algorithm for filling shells with electrons. First, they enter the upper layer (s-orbital), and only after it is completely filled, the electrons enter the shell located below (d-orbital).
The large-scale use of ferromagnets, the main of which is iron, is explained by the change in structure when exposed to an external magnetic field.
Similar properties can only be possessed by those substances in the atoms of which there are internal unfinished shells. But even this condition is not enough to talk about ferromagnetic characteristics. For example, chromium, manganese, platinum also haveunfinished shells inside atoms, but they are paramagnetic. The occurrence of spontaneous magnetization is explained by a special quantum action, which is difficult to explain using classical physics.
Department
There is a conditional 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 in the creation of electromagnets, transformer cores. The differences between the two species are explained by the peculiarities of the chemical structure of these substances.
Features of use
Let's take a closer look at 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.
Rigid types are needed to create permanent magnets. If the external field is turned off, ferromagnets retain their properties, since the orientation of elementary currents does not disappear.
It is this property that explains the use of ferromagnets. In short, we can say 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
Considering the use of ferromagnets, it is necessary to pay special attention to ferrites. They are widely used in high-frequency radio engineering, since they combine the properties of semiconductors and ferromagnets. It is from ferrites that magnetic tapes and films, cores of inductors, and disks are currently made. They are iron oxides found in nature.
Interesting facts
Interest is the use of ferromagnets in electrical machines, as well as in the technology of recording in a hard drive. Modern research suggests that at certain temperatures, some ferromagnets can acquire paramagnetic characteristics. That is why these substances are considered poorly understood 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 manifests itself in ferromagnets, as well as in alloys made of iron, nickel, cob alt. A similar phenomenon is observed not only in the case of a change in the direction and magnitude of the field, but also in the case of its rotation.
Permeability
Magnetic permeability is a physical quantity that shows the ratio of induction in a certain medium to that in a vacuum. If a substance creates its own magnetic field, it is considered magnetized. According to Ampère's hypothesis, the value of properties depends on the orbital motion of "free" electrons in the atom.
The hysteresis loop is a curve of the dependence 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 used body, you need to change the direction of the external magnetic field.
At a certain value of magnetic induction, which is called the coercive force, the magnetization of the sample becomes zero.
It is the shape of the hysteresis loop and the magnitude of the coercive force that determine the ability of a substance to maintain partial magnetization and explain the widespread use of ferromagnets. Briefly, the areas of application of hard ferromagnets with a wide hysteresis loop are described above. Tungsten, carbon, aluminum, chromium steels have a large coercive force, therefore, permanent magnets of various shapes are created on their basis: strip, horseshoe.
Among soft materials with a small coercive force, we note iron ores, as well as iron-nickel alloys.
The process of magnetization reversal of ferromagnets is associated with a change in the region of spontaneous magnetization. For this, the work done by the external field is used. Quantitythe 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 technological 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, allow you to fully automate the most labor-intensive technological processes, as well as significantly speed up the process of assembling new vehicles.
In radio engineering, ferromagnets make it possible to obtain devices of the highest quality and accuracy.
Scientists have succeeded in creating a one-step method for manufacturing magnetic nanoparticles that are suitable for applications in medicine and electronics.
As a result of numerous studies carried out in the best research laboratories, it was possible to establish the magnetic properties of cob alt and iron nanoparticles coated with a thin layer of gold. Their ability to transfer anti-cancer drugs or radionuclide atoms to the right part of the human body and increase the contrast of magnetic resonance images has already been confirmed.
In addition, such particles can be used to upgrade magnetic memory devices, which will be a new step in creating an innovativemedical technology.
A team of Russian scientists managed to develop and test a method for reducing aqueous solutions of chlorides to obtain combined cob alt-iron nanoparticles suitable for creating materials with improved magnetic characteristics. All research conducted by scientists is aimed at improving the ferromagnetic properties of substances, increasing their percentage use in production.
