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The source of magnetic properties of NdFeB magnets

First, the origin of the magnetism of matter If the magnetism of a magnet is an electromagnetic ether vortex, a magnet, does not see any electromagnetic ether vortex, why is there magnetism? Our answer is: the magnetism of matter originates from the movement of electrons in atoms, and the movement of electrons produces an electromagnetic ether vortex. As early as 1820, Danish scientist Oster discovered the magnetic effect of current, and for the first time revealed the connection between magnetism and electricity, thus linking electricity and magnetism. In order to explain the phenomenon of permanent magnets and magnetization, Ampere proposed the molecular current hypothesis. Ampere believes that there is a ring current in the molecules of any substance, called molecular current, and


The origin of magnetism of 1. matter

If the magnetism of a magnet is an electromagnetic etheric vortex, a magnet that doesn't see any electromagnetic etheric vortex, why is there magnetism? Our answer is: the magnetism of matter originates from the movement of electrons in atoms, and the movement of electrons creates an electromagnetic etheric vortex.

Early inIn 1820, Danish scientist Oster discovered the magnetic effect of current, revealing for the first time that there is a connection between magnetism and electricity, thus linking electricity and magnetism.

In order to explain the phenomenon of permanent magnets and magnetization, Ampere proposed the molecular current hypothesis. Ampere believes that there is a circular current in the molecules of any substance, called a molecular current, and the molecular current is equivalent to a primitive magnet. When there is no magnetism in the macroscopic material, the orientation of these molecular currents is irregular, and their magnetic effects on the outside world cancel each other out, so the whole object is not magnetic. Under the action of an external magnetic field, the individual molecular currents equivalent to the primitive magnet will tend to be oriented in the direction of the external magnetic field, causing the object to exhibit magnetism.

There is an essential connection between magnetic phenomena and electric phenomena. The magnetism of matter is closely related to the movement structure of electrons. The concept of electron spin first proposed by Uhlenbeck and Goldsmith is to regard electrons as a charged ball. They believe that, similar to the movement of the earth around the sun, electrons on the one hand revolve around the atomic nucleus with orbital angular momentum and orbital magnetic moment, on the other hand, electrons rotate around their own axis with spin angular momentum and corresponding spin magnetic moment. Stern-The magnetic moment that Gerach measured from the silver atomic ray experiment is this spin magnetic moment. (It is now believed that it is incorrect to regard the electron spin as the rotation of the ball around its own axis.)

The circular orbit of electrons around the atomic nucleus and the spin movement around itself will produce the vortex of electromagnetic ether to form magnetism. People often use magnetic moment to describe magnetism. Therefore, the electron has a magnetic moment, and the electron magnetic moment is composed of the orbital magnetic moment and the spin magnetic moment of the electron. In the crystal, the orbital magnetic moment of the electron is affected by the lattice, and its direction is changed, and a joint magnetic moment cannot be formed, and there is no magnetic effect on the outside. Therefore, the magnetism of matter is not caused by the orbital magnetic moment of electrons, but mainly by the spin magnetic moment. The approximate value of the magnetic moment of each electron spin is equal to a Bohr magneton . is the unit of atomic magnetic moment, . Because atomic nuclei are heavier than electronsAbout 2000 times, its movement speed is only a few 1‰ of the electron speed, so the magnetic moment of the nucleus is only a few thousandths of the electron, which can be ignored.

The magnetic moment of an isolated atom is determined by the structure of the atom. If there is an unfilled electron shell in an atom, the spin magnetic moment of its electrons is not canceled, and the atom has"Permanent magnetic moment". For example, the atomic number of an iron atom is 26, with a total of 26 electrons. Except for one of the five orbitals that must be filled with two electrons (spin antiparallel), the other four orbitals have only one electron, and the spin directions of these electrons are parallel, thus the total electron spin magnetic moment is 4.

II, Classification of magnetic properties of substances

1. Anti-magnetism

When the magnetizationWhen M is negative, the solid appears diamagnetic. Metals such as Bi, Cu, Ag, and Au have such properties. In the external magnetic field, the magnetic induction intensity inside the magnetized medium is less than the magnetic induction intensity M in the vacuum. The magnetic moment of an atom (ion) of a diamagnetic substance should be zero, that is, there is no permanent magnetic moment. When a diamagnetic substance is placed in an external magnetic field, the external magnetic field changes the electron orbit and induces a magnetic moment opposite to the direction of the external magnetic field, which is manifested as diamagnetism. So the diamagnetism comes from the change of the state of the electron orbit in the atom. The diamagnetic material is generally very weak, and the magnetic susceptibility H is generally about -10-5, which is negative.

2. paramagnetic

The main characteristic of paramagnetic substances is the existence of a permanent magnetic moment inside the atom, whether or not there is an applied magnetic field. However, in the absence of an external magnetic field, because the atoms of paramagnetic substances do irregular thermal vibrations, macroscopically, there is no magnetism; under the action of an external magnetic field, the magnetic moment of each atom is relatively regularly oriented, and the substance shows extremely weak magnetism. The magnetization is in the same direction as the external magnetic field,

positive, and strictly related to the external magnetic fieldH is proportional.

The magnetic properties of paramagnetic substances in additionH is also dependent on temperature. Its magnetic susceptibility H is inversely proportional to the absolute temperature T.

In the formula, C is called the Curie constant, which depends on the magnetization and magnetic moment of the paramagnetic substance.

The magnetic susceptibility of paramagnetic substances is generally very small, and at room temperatureH is about 10-5. Generally, atoms or molecules containing an odd number of electrons, atoms or ions that do not fill the shell, such as transition elements, rare earth elements, steel elements, and metals such as aluminum and platinum, are all paramagnetic substances.

3. Ferromagnetism

For suchFe, Co, Ni and other substances, at room temperature, the magnetic susceptibility of up to 10-3 orders of magnitude, said that the magnetic properties of such substances for ferromagnetism.

Ferromagnetic materials can obtain extremely high magnetization even in a weak magnetic field, and when the external magnetic field is removed, they can still retain extremely strong magnetism. The magnetic susceptibility is positive, but when the external field increases, because the magnetization quickly reaches saturation, itsH becomes smaller.

Ferromagnetic materials have strong magnetic properties, mainly due to their strong internal exchange field. The exchange energy of ferromagnetic substances is positive and large, so that the magnetic moments of adjacent atoms are oriented parallel (corresponding to the stable state), forming many small regions inside the substance-- Magnetic domain. Each magnetic domain has about 1015 atoms. The magnetic moments of these atoms are arranged in the same direction, assuming that there is a strong internal field called the "molecular field" inside the crystal, which is sufficient to automatically magnetize each magnetic domain to a saturated state. This spontaneous magnetization is called spontaneous magnetization. Because of its existence, ferromagnetic substances can be magnetized strongly in a weak magnetic field. Therefore, spontaneous magnetization is the basic feature of ferromagnetic substances, and it is also the difference between ferromagnetic substances and paramagnetic substances.

The ferromagnetism of a ferromagnet is manifested only below a certain temperature, above which the spontaneous magnetization becomes due to the destruction of the parallel orientation of the electron spin magnetic moment by thermal turmoil within the substance.0, ferromagnetic disappeared. This temperature is called the Curie point. Above the Curie point, the material is strongly paramagnetic, and the relationship between its magnetic susceptibility and temperature obeys the Curie-Wais law,

In the formulaC is the Curie constant.

4. Antiferromagnetism

Antiferromagnetism refers to the antiparallel arrangement of electron spins. There is spontaneous magnetization in the same sub-lattice, and the electronic magnetic moments are aligned in the same direction; in different sub-lattices, the electronic magnetic moments are aligned in the opposite direction. The spontaneous magnetization in the two sub-lattices is the same in magnitude and opposite in direction, and the entire crystal . Antiferromagnetic substances are mostly non-metallic compounds, suchMnO。

No matter at what temperature, no spontaneous magnetization of antiferromagnetic substances can be observed, so its macroscopic properties are paramagnetic,M and H are in the same direction, and the magnetic susceptibility is positive. When the temperature is very high, it is very small; the temperature decreases and gradually increases. At a certain temperature, the maximum value is reached. It is called the Curie point or Neil point of an antiferromagnetic substance. The explanation for the existence of the Neil point is that at very low temperatures, because the spins of adjacent atoms are completely reversed, their magnetic moments are almost completely canceled, so the magnetic susceptibility is almost close to 0. When the temperature rises, the effect of reversing the spin weakens and increases. When the temperature rises above the Neil point, the influence of thermal agitation is greater, and the antiferromagnet has the same magnetization behavior as the paramagnetic body.

Relationship between orbital magnetic moment and orbital angular momentum of 3. electron

Set the track radiusr (circular orbit), electron velocity is v

then the track currentI:

orbital magnetic moment of an electron

For an electron in the ground state of a hydrogen atom,

the orbital angular momentum of an electron(circular orbit)

L = mvr

In the formulam is the electron mass

Since the electrons are negatively charged, the relationship between the orbital magnetic moment of the electron and the orbital angular momentum is:

(Although this formula is derived from circular orbits, it is the same as the conclusion of quantum mechanics)

It is particularly emphasized here that the orbital magnetic moment of the electron is proportional to the orbital angular momentum.

IV. Relationship between spin magnetic moment and spin angular momentum

Experiments show that electrons have spin(intrinsic) motion, the corresponding spin magnetic moment size is

spin magnetic moment and spin angular momentumS relationship:

It is particularly emphasized here that the magnetic moment of the electron spin is in turn proportional to the spin angular momentum. It is not accidental that the magnetic moment is proportional to the angular momentum. Because the greater the angular momentum of the electron, the greater the angular momentum of the electromagnetic ether vortex it drives, and the greater the magnetic moment of course. This also confirms that magnetism is a vortex of ether from the other side.

Source: magnet manufacturers Youlian Magnetic Industrywww.youliancy.com

 

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