What are the classifications of magnetic materials

Magnetic materials are ferromagnetic substances with magnetic order, and also include weak magnetic and antiferromagnetic substances to which their magnetic and magnetic effects can be applied in a broad sense. Magnetism is a fundamental property of matter. Substances can be divided into diamagnetic, paramagnetic, ferromagnetic, antiferromagnetic and ferrimagnetic substances according to their internal structure and their properties in an external magnetic field. Ferromagnetic and ferrimagnetic substances are strong magnetic substances, and diamagnetic and paramagnetic substances are weak magnetic substances. Magnetic materials are divided into two categories: metal and non-metal according to their properties. The former mainly include electrical steel, nickel-based alloys and rare earth alloys, and the latter are mainly ferrite materials. According to the use, it is divided into soft magnetic materials, permanent magnetic materials and functional magnetic materials. Functional magnetic materials mainly include magnetostrictive materials, magnetic recording materials, magnetoresistive materials, magnetic bubble materials, magneto-optical materials, gyromagnetic materials and magnetic film materials, etc. The basic magnetic properties of magnetic materials are reflected by magnetization curves and hysteresis loops. and magnetic loss, etc. Permanent magnet materials, after being magnetized by an external magnetic field, can still maintain a part or most of the magnetism in the original magnetization direction even under the action of a relatively large reverse magnetic field. The requirements for this type of material are high residual magnetic induction intensity Br, strong coercivity BHC (that is, anti-demagnetization ability), and large magnetic energy product (BH), that is, the magnetic field energy provided to the space). Compared with soft magnetic materials, it is also called hard magnetic materials. There are three types of permanent magnet materials: alloys, ferrites and intermetallic compounds. ①Alloys: including casting, sintering and machinable alloys. The main varieties of cast alloys are: AlNi (Co), FeCr (Co), FeCrMo, FeAlC, FeCo (V) (W); sintered alloys are: Re-Co (Re represents rare earth elements), Re-Fe and AlNi (Co ), FeCrCo, etc.; Machinable alloys are: FeCrCo, PtCo, MnAlC, CuNiFe and AlMnAg, etc. The latter two with lower BHC are also called semi-permanent magnet materials. ② Ferrites: the main components are MO6Fe2O3, M represents Ba, Sr, Pb or SrCa, LaCa and other composite components. ③Intermetallic compounds: mainly represented by MnBi. Permanent magnet materials have a variety of uses. ①The main applications based on the principle of electromagnetic force are: speakers, microphones, electricity meters, buttons, motors, relays, sensors, switches, etc. ②The applications based on the principle of magnetoelectric action mainly include: microwave electron tubes such as magnetrons and traveling wave tubes, picture tubes, titanium pumps, microwave ferrite devices, magnetoresistive devices, Hall devices, etc. ③The main applications based on the principle of magnetic force are: magnetic bearings, mineral concentrators, magnetic separators, magnetic chucks, magnetic seals, magnetic blackboards, toys, signs, password locks, copiers, thermometers, etc. Other applications include: magnetic therapy, magnetized water, magnetic anesthesia, etc. According to the needs of use, permanent magnet materials can have different structures and shapes. Some materials are also isotropic and anisotropic. Soft magnetic material, its function is mainly to conduct magnetic, electromagnetic energy conversion and transmission. Therefore, such materials are required to have higher magnetic permeability and magnetic induction intensity, and at the same time, the area or magnetic loss of the hysteresis loop should be small. Contrary to permanent magnet materials, the smaller the Br and BHC, the better, but the larger the saturation magnetic induction intensity Bs, the better. A kind of soft magnetic material - iron powder core. Soft magnetic materials can be roughly divided into four categories. ①Alloy strip or sheet: FeNi (Mo), FeSi, FeAl, etc. ②Amorphous alloy ribbons: Fe-based, Co-based, FeNi-based or FeNiCo-based with appropriate Si, B, P and other doping elements, also known as magnetic glass. ③ Magnetic medium (iron powder core): FeNi (Mo), FeSiAl, carbonyl iron, ferrite and other powders, after being coated and bonded by an electrical insulating medium, are pressed and formed as required. ④ Ferrite: including spinel type ─ M OFe2O3 (M stands for NiZn, MnZn, MgZn, Li1/2Fe1/2Zn, CaZn, etc.), magnetoplumbite type ─ Ba3Me2Fe24O41 (Me stands for Co, Ni, Mg, Zn, etc.) , Cu and its composite components). Soft magnetic materials are widely used, mainly for magnetic antennas, inductors, transformers, magnetic heads, headphones, relays, vibrators, TV deflection yokes, cables, delay lines, sensors, microwave absorbing materials, electromagnets, accelerators for high-frequency acceleration Cavity, magnetic field probe, magnetic substrate, magnetic field shielding, high-frequency quenching energy, electromagnetic chuck, magnetic sensitive element (such as magneto-caloric material as switch), etc. Magnetic moment and magnetic recording material, mainly used for information recording, contactless switch, logic operation and information amplification. This material is characterized by a rectangular hysteresis loop. Gyromagnetic materials have 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 according to this are mainly used for the transmission and conversion of microwave energy, commonly used are isolators, circulators, filters (fixed or ESC), attenuators, phase shifters, modulators, switches, limiters and Delay lines, etc., and still developing surface magnetostatic wave and magnetostatic wave devices (see microwave ferrite devices). Commonly used materials have formed a series, including Ni series, Mg series, Li series, YlG series and BiCaV series and other ferrite materials; and can be made into different structures such as single crystal, polycrystalline, amorphous or thin film according to the needs of the device and form. Piezomagnetic material, which is characterized by mechanical deformation under the action of an external magnetic field, so it is also called magnetostrictive material, and its function is to convert magneto-acoustic or magnetic energy. Commonly used in vibrating heads of ultrasonic generators, mechanical filters of communication machines and delay lines of electrical pulse signals, etc., combined with microwave technology, micro-acoustic (or whirling) devices can be produced. Due to the high mechanical strength of the alloy material, it is resistant to vibration without bursting, so Ni-based and NiCo-based alloys are mostly used for the vibrating head; Ni-based and NiCo-based ferrites are mostly used for small signals. A new type of amorphous alloy with strong piezomagnetism is suitable for making delay lines. The production and application of piezomagnetic materials are far less than the previous four materials. Applications of Magnetic Materials - Transformers. Magnetic materials are widely used materials in production, life, and national defense science and technology. Such as the manufacture of various motors and transformers in power technology, various magnetic components and microwave tubes in electronic technology, filters and intensifiers in communication technology, magnetic mines, electromagnetic guns in national defense technology, various household appliances, etc. . 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. It mainly uses its various magnetic properties and special effects to make components or devices; it is used to store, transmit and convert electromagnetic energy and information, or to generate a certain intensity and distribution of magnetic fields in a specific space; sometimes it is also directly used in the natural form of the material. use (eg magnetic liquids). Magnetic materials play an important role in electronic technology and other fields of science and technology.