Classification of magnetic materials

Magnetic materials have strong magnetic materials with magnetic order, and generally include weak magnetic and antiferromagnetic materials that can apply their magnetism and magnetic effects. Magnetism is a basic property of matter. Materials can be divided into diamagnetic, paramagnetic, ferromagnetic, antiferromagnetic and ferrimagnetic materials according to their internal structure and properties in the external magnetic field. Ferromagnetic and ferrimagnetic substances are strong magnetic substances, and diamagnetic and paramagnetic substances are weak magnetic substances. Magnetic materials can be divided into metal and nonmetal according to their properties. The former mainly includes electrical steel, nickel base alloy and rare earth alloy, while the latter mainly includes ferrite materials. According to the use, it can be divided into soft magnetic materials, permanent magnetic materials and functional magnetic materials. Functional magnetic materials mainly include magnetostrictive materials, magnetic recording materials, magnetoresistance materials, magnetic bubble materials, magneto-optical materials, gyromagnetic materials and magnetic film materials. The basic magnetic properties of magnetic materials are reflected by magnetization curves, hysteresis loops and magnetic losses.
1. Permanent magnet materials
Once magnetized by an external magnetic field, the permanent magnetic material can still maintain a part or most of the original magnetization direction even under the action of a relatively large reverse magnetic field. The requirements for such materials are high residual magnetic induction strength Br, strong coercive force BHC (i.e., anti demagnetization ability of magnetic materials), and large magnetic energy product (BH) (i.e., magnetic field energy provided for space). Compared with soft magnetic materials, it is also called hard magnetic materials.
Permanent magnetic materials include alloy, ferrite and intermetallic compound. ① Alloys: including cast, sintered and machinable alloys. The main varieties of casting alloys are: AlNi (Co), FeCr (Co), FeCrMo, FeAlC, FeCo (V) (W); Sintered alloys include Re Co (Re represents rare earth element), Re Fe, AlNi (Co), FeCrCo, etc; Machinable alloys include FeCrCo, PtCo, MnAlC, CuNiFe and AlMnAg. The latter two are also called semi permanent magnetic materials with lower BHC. ② Ferrites: the main component is MO · 6Fe2O3, and M represents Ba, Sr, Pb or SrCa, LaCa and other composite components. ③ Intermetallic compounds: mainly represented by MnBi.
Permanent magnet materials have many uses: ① Applications based on the principle of electromagnetic force mainly include: speakers, microphones, meters, buttons, motors, relays, sensors, switches, etc. ② The applications based on the principle of magnetoelectric action mainly include microwave electron tubes such as magnetron and traveling wave tube, picture tubes, titanium pumps, microwave ferrite devices, magnetoresistive devices, Hall devices, etc. ③ Applications based on the principle of magnetic force mainly include: magnetic bearing, concentrator, magnetic separator, magnetic chuck, magnetic seal, magnetic blackboard, toy, sign, password lock, copier, temperature controller, etc. Other applications include: magnetic therapy, magnetized water, magnetic anesthesia, etc.
According to the needs of use, permanent magnetic materials can have different structures and shapes. Some materials are also isotropic and anisotropic.
2. Soft magnetic materials
Its function is mainly the conversion and transmission of magnetic conductivity and electromagnetic energy. Therefore, high permeability and magnetic induction strength are required for such materials, and the area of hysteresis loop or magnetic loss is small. Contrary to permanent magnetic materials, the smaller the Br and BHC, the better, but the larger the saturated magnetic induction strength Bs, the better.
A Kind of Soft Magnetic Material -- Iron Powder Core
Soft magnetic materials can be generally divided into four categories. ① Alloy strip or sheet: FeNi (Mo), FeSi, FeAl, etc. ② Amorphous alloy ribbons: Fe based, Co based, FeNi based or FeNiCo based ribbons are matched with appropriate Si, B, P and other doped elements, which are also called magnetic glasses. ③ Magnetic medium (iron powder core): FeNi (Mo), FeSiAl, carbonyl iron, ferrite and other powders, which are pressed and formed as required after being coated and bonded by electrical insulating medium. ④ Ferrite: including spinel type - M O · Fe2O3 (M represents NiZn, MnZn, MgZn, Li1/2Fe1/2Zn, CaZn, etc.), and magnetic lead type - Ba3Me2Fe24O41 (Me represents Co, Ni, Mg, Zn, Cu and their composite components). Soft magnetic materials are widely used, mainly for magnetic antennas, inductors, transformers, magnetic heads, earphones, relays, vibrators, TV deflection yokes, cables, delay lines, sensors, microwave absorbing materials, electromagnets, accelerator high-frequency accelerating cavities, magnetic field probes, magnetic substrates, magnetic field shielding, high-frequency quenching and energy gathering, electromagnetic suction cups, magnetic sensitive elements (such as magnetothermic materials as switches), etc.
3. Moment magnetic materials and magnetic recording materials
It is mainly used for information recording, contactless switch, logic operation and information amplification. This material is characterized by a rectangular hysteresis loop.
4. Rotating magnetic materials
It has unique microwave magnetism, such as tensor properties of permeability, Faraday rotation, resonance absorption, field shift, phase shift, birefringence and spin wave effects. The devices designed on this basis are mainly used for the transmission and conversion of microwave energy, commonly used are isolators, circulators, filters (fixed or electrically modulated), attenuators, phase shifters, modulators, switches, limiters and delay lines, as well as magnetic surface wave and magnetostatic wave devices that are still in development (see microwave ferrite devices). A series of commonly used materials have been formed, including Ni series, Mg series, Li series, YlG series, BiCaV series and other ferrite materials; It can be made into single crystal, polycrystal, amorphous or thin film and other different structures and shapes according to the needs of devices.
5. Piezomagnetic materials
This kind of material is characterized by mechanical deformation under the action of external magnetic field, so it is also called magnetostrictive material. Its function is to convert magnetoacoustic or magnetic energy. It is commonly used for vibrating head of ultrasonic generator, mechanical filter of communication machine, delay line of electric pulse signal, etc. It can be combined with microwave technology to make micro acoustic (or rotary acoustic) devices. Due to the high mechanical strength and vibration resistance of alloy materials, Ni series and NiCo series alloys are mostly used for vibration heads; Ni series and NiCo series ferrites are mostly used under small signal. The new varieties of amorphous alloys with stronger piezomagnetism are suitable for making delay lines. The production and application of piezomagnetic materials are far less than the previous four materials.
Application of Magnetic Materials Transformer
Magnetic materials are widely used in production, life and national defense science and technology. Such as manufacturing various motors and transformers in electric power technology, various magnetic components and microwave tubes in electronic technology, filters and inductors in communication technology, magnetic mines and electromagnetic guns in national defense technology, and various household appliances. In addition, magnetic materials have also been widely used in geological and mineral exploration, ocean exploration, and new technologies in information, energy, biology and space. Magnetic materials are widely used. They are mainly made into components or devices by using their various magnetic properties and special effects; It is used to store, transmit and convert electromagnetic energy and information, or generate a certain intensity and distribution of magnetic field in a specific space; Sometimes it is also directly used in the natural form of materials (such as magnetic fluid). Magnetic materials play an important role in the field of electronic technology and other scientific and technological fields.