As long as a small amount of metal is the magnetic
The source of the magnetic material
If magnetic is electromagnetic etheric vortex, a magnet, didn't see any electromagnetic vortex of Ethernet, why there will be magnetic? Our answer is: the material of magnetic from the movement of the electrons in the atoms, electronic games happen a electromagnetic vortex of Ethernet.
As early as in 1820, Danish scientists have found that the current magnetic oster, for the first time is a reminder of the magnetic and electrical contact, and then the electricity and magnetism contact up.
In order to define the permanent magnet and magnetic picture, ampere molecular current hypothesis was put forward. Ampere thought, any material ring current exist in molecules, known as molecular electric current, and appropriate molecular current a primitive magnets. When the material does not exist on the micro magnetic orientation is made of these molecular current without rules, they what happens on the outside magnetic cancel each other out, so that all objects not magnetic. Under the effect of outer magnetic field, the equivalent base yuan magnets to each molecule current will tend to orientation along the external magnetic field direction, and make the object appear magnetism.
Magnetic sight scene and electricity have real contact. The movement of material of magnetic and electronic structure has the close relation. Wu Aaron beck and gothic schmidt first put forward the concept of electron spin is the electronics as a charged balls, they think, is similar to the earth's movement round the sun, the electrons around the nucleus work on the one hand, the corresponding trajectory magnetic moment and angular momentum, around its own axis rotation again on the other hand, has spin angular momentum and spin magnetic moment. Grace - straw cover lage from measured the magnetic moment of silver atoms ray tests are just the spin magnetic moment. (now everybody thought that the electron spin as a ball around its own axis of rotation is incorrect.)
Electrons around the nucleus circular trajectory work happens all the time and the movement of the spin around its electromagnetic etheric vortex and a magnetic, commonly used to describe the magnetic magnetic moment. And therefore has a magnetic moment, electronic magnetic moment is composed of electronic track magnetic moment and the spin magnetic moment. In the crystal, electronic track magnetic moment by the effect of lattice, its direction is changed, don't make a combined magnetic moment, foreign has no magnetic effect. Thus, the magnetic substance is not caused by the electron trajectory magnetic moment, but first caused by spin magnetic moment. Each electron spin magnetic moment of approximation is a Bohr magneton. Is the unit of atomic magnetic moment. Because the nucleus is 2000 times heavier than the electron, its movement speed is only electronic speed is one of the thousands of points, so the nucleus of only a few parts per thousand for the electronic, magnetic moment can be neglected.
The magnetic moment of isolated atom is determined by the structure of the atom. If have not been filled in the atomic electron shell, the electronic spin magnetic moment has not been offset by atom will have a "permanent magnetic moment". Iron atoms of the atomic number of 26, for example, a total of 26 electrons, in addition to a track in five trajectory is necessary to fill in the two electronic (spin antiparallel), the other four tracks are as long as an electron, and the electronic spin direction parallel to the total electron spin magnetic moment of 4.
Ferromagnetic sights found early, but the sight of essential factors and laws, is still just beginning to know at the beginning of this century. 1907 French scientists outside system proposed the ferromagnetic hypothesis, the primary contents are as follows: ferromagnetic material within the very strong "molecular field", under the effect of "molecular field", atomic magnetic moment tend to be parallel to the direction, the magnetization consciously to full, called consciously magnetization; Ferromagnet magnetized consciously dividends several small regions (the magnetization consciously to full of small area is called the magnetic domain), because each area (domain) the magnetization direction of each are not identical, its magnetic cancel each other out to each other, so the bulk ferromagnetic foreign appeared not magnetic.
Outside the assumptions made a great success, experiment proves its correctness, and on the basis of the modern theory of ferromagnetism. On the basis of the hypothesis of molecular field, carried out consciously magnetization (what magnetization) theory, the explanation of the ferromagnetic substance; Conducted on the basis of the hypothesis of magnetic domain skills magnetization theory, explains the ferromagnetic behavior in magnetic field.
Ferromagnetic materials magnetic is unconscious. So-called magnetization process (also called sense magnetic magnetization) or just the magnetism of the material itself appeared, rather than from the outside to the process of magnetic material supply. Tests prove that the ferromagnetics consciously magnetization atoms (ions) magnetic moment in origin, and the primary effect in atomic magnetic moment of electron spin magnetic moment. Same as the paramagnetic atom, the atom electronic shell is not exist in filling condition is a necessary condition of ferromagnetic.
Such as 3 d status of iron has four slots, 3 d status of cobalt has three empty seats, the nickel 3 d state has two slots. If make filling the electron spin magnetic moment of press direction is put up, will get a large magnetic moment, the theory of feng has 4 mu B, has three mu B cobalt, nickel has 2 mu B.
But for some transition elements, such as manganese has five slots on 3 d state, if the synthetic put, they spin magnetic moment should be 5 mu B, but it's not a ferromagnetic elements. Therefore, exist in the atoms are not electronic filling condition (d or f state) is a necessary condition of ferromagnetic, but not sufficient condition. Is not just so happened ferromagnetic element of atomic magnetic moment is high, and think about crystal formation, the each other between atomic bonding effect is not good for constitute a ferromagnetic. This is the second condition of constitute a ferromagnetic.
On bond theory, the atomic approached each other constitute molecules, electron cloud stack with each other, electrons to communicate with each other. About transition metal, atomic energy of the status of the 3 d and s state were similar, so it's electron cloud will also be stacked, s, d status of electronic redistribution. A kind of communication can the communication occurs Eex (related to exchange points), the can communication has the potential to adjacent atoms within d layer offset at the end of the spin magnetic moment Direction is put up.
Quantum mechanics calculation indicate, when magnetic materials internal timing of the adjacent atom electronic communication integral (A) > 0, adjacent atomic magnetic moment will be parallel to the direction, then complete the magnetization consciously. This is the factor of ferromagnetic occurred. The adjacent atom electronic communication effect, its essence is still the electrostatic force force parallel to the electron spin magnetic moment, the same effect as the effect of magnetic field. Weiss molecular field is so named.
Integral A theoretical calculation proves that the communication is not only related to electronic movement condition of the wave function, and is strongly dependent on the gap between the sub atomic nuclei Rab (lattice constant), as shown in figure 5 to 13. By figure can be seen, as long as when the interval between the nucleus Rab involved in electronic communication effect from nuclear intervals (electron shell radius r is greater than 3, communication integration can help is. Iron, cobalt, nickel and some rare earth elements satisfied consciously magnetization conditions. Chromium, manganese is A negative value, not A ferromagnetic metal, but through the effect of alloying, alter the lattice constant, makes the Rab/r ratio of greater than 3 and ferromagnetic alloy can be got.
To sum up, ferromagnetism of conditions:
(1) the atomic internal to fill at the end of the electron shell;
(2) and the ratio of the Rab/r is greater than 3 make integral A positive communication. The former refers to the atomic intrinsic magnetic moment is zero; The latter refers to is to have a certain crystal structure.
Based on the theory of magnetization process and consciously, can explain a lot of ferromagnetic properties. For example, the influence of temperature on the ferromagnetic. When the temperature increases, the atomic distance increase, reduce the communication effect, thermal motion with constant damage The rules of the atomic magnetic moment orientation, so self-conscious magnetization Ms decline. Until the temperature higher than the Curie point, so as to thoroughly broken the rules of the atomic magnetic moment orientation, consciously magnetic moment does not exist, data from ferromagnetism to paramagnetism. The same, can explain magnetocrystalline anisotropy, magneto elasticity, etc.
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