Common magnetic properties of magnetic materials:

1. Saturation magnetic induction intensity Bs: Its size depends on the composition of the material, and its corresponding physical state is the orderly arrangement of magnetization vectors inside the material.

2. Residual magnetic induction intensity Br: is the characteristic parameter on the hysteresis loop, and the Value of B when H returns to 0.

3. Rectangle ratio: Br/Bs. Coercivity Hc: the amount that indicates the difficulty in magnetizing a material, depending on its composition and defects (impurities, stresses, etc.).

4. Permeability: the ratio of B to H corresponding to any point on the hysteresis loop, which is closely related to the working state of the device.

5, initial permeability I, maximum permeability m, differential permeability D, amplitude permeability a, effective permeability E, pulse permeability P.

6. Curie temperature Tc: The magnetization of ferromagnetic material decreases with the increase of temperature. When a certain temperature is reached, the spontaneous magnetization disappears and becomes paramagnetism. It determines the upper operating temperature of magnetic devices.

7, loss P: hysteresis loss Ph and eddy current loss Pe P = Ph + Pe = AF + BF2 + C Pe ∝ f2 T2 /, decrease, hysteresis loss Ph is reduced coerce Hc; The eddy current loss of Pe is reduced by thinning the thickness t of the magnetic material and increasing the resistivity of the material.

The relationship between core loss and core temperature rise in free still air is as follows: total power dissipation (mW)/surface area (Cm2).

Consumer Guide:

(1) High residual magnetic induction intensity Br. Because Br high to ensure that the motor has a high speed, large output torque and large power. The motor will have higher efficiency.

(2) High Hcb. Because of the high Hcb, the required ELECTROmotive force output of the motor can be ensured, so that the working point of the motor is close to the maximum magnetic energy product, and the ability of the magnet can be fully utilized.

(3) High Hcj. High Hcj can ensure that the motor has strong anti-overload demagnetization and anti-aging, anti-low temperature ability.

(4) High (BH) Max. (BH) The higher the Max, the better the actual operating coefficient of ferrite tile in the motor.

(5) magnetic energy Φ the bigger the better, this will greatly improve the work efficiency of the machine.

(6) The better the rectangularity of demagnetization curve is, the smaller the dynamic loss of the motor will be.

(7) The higher the resistivity of ferrite tile, the smaller the eddy current loss.

(8) Ferrite magnetic tile has a small temperature coefficient, and has good temperature stability at high temperature.

The magnetization curve of a magnetic material

Magnetic materials are composed of ferromagnetic materials or ferromagnetic materials. Under the action of external magnetic field H, there must be corresponding magnetization intensity M or magnetic induction intensity B. Their curve of change with magnetic field intensity H is called magnetization curve (M ~ H or B ~ H curve). Generally speaking, the magnetization curve is nonlinear and has two characteristics: magnetic saturation and hysteresis. That is, when the magnetic field intensity H is large enough, the magnetization intensity M reaches a certain saturation value Ms, and continues to increase H while Ms remains unchanged. And when the material's M value reaches saturation and the external magnetic field H decreases to zero, M does not recover to zero, but changes along the MsMr curve. The working state of the material is equivalent to a point on the M-H curve or B-H curve, which is often referred to as the working point.

Conversion between magnetic parameters of soft magnetic materials and electrical parameters of devices

In the design of soft magnetic devices, the voltage - current characteristics of the devices should be determined according to the requirements of the circuit. The voltage - current characteristics of the device are closely related to the geometry and magnetization state of the magnetic core. The designer must be familiar with the magnetization process of the material and hold the conversion relationship between the magnetic parameters of the material and the electrical parameters of the device. Designing soft magnetic devices usually involves three steps: selecting magnetic materials correctly; Reasonably determine the geometry and size of the magnetic core; According to the requirements of magnetic parameters, the corresponding electrical parameters are obtained by simulating the working state of the magnetic core.

Magnetic material is an important electronic material. The early magnetic materials mainly used metal and alloy system, with the development of production, in the power industry, telecommunications engineering and high-frequency radio technology, there is an urgent need to provide a high resistivity of magnetic materials with high efficiency. On the basis of restudying magnetite and other magnetic oxides, a new magnetic material ferrite has been developed. Ferrite belongs to the magnetic material of oxide system. It is a composite oxide composed mainly of iron oxide and other iron group elements or oxides of rare earth elements. It can be used to produce various functional devices for energy conversion, transmission and information storage.

Ferrite magnetic materials can be divided into spinel type (MFe2O4) according to their crystal structure. Garnet type (R3Fe5O12); Magnetic lead-stone type (MFe12O19); Perovskite type (MFeO3). Where M refers to the bivalent metal ion with a radius close to that of Fe2+, and R is a rare earth element. According to the different USES of ferrite, it can be divided into soft magnetism, hard magnetism, moment magnetism and pressure magnetism, etc.

Soft magnetic material refers to a ferrite material which is easy to magnetize and demagnetize under a weak magnetic field. The soft magnetic ferrite with practical value is mainly Mn-ZnFe2O4 and Ni-ZnFeO4. The crystal structure of soft magnetic ferrite is generally of cubic spinel type, which is a kind of material with wide application, large quantity, more varieties and higher output value among various ferrites at present. Mainly used for various inductance components, such as filter, transformer and antenna magnetic and magnetic tape recording and video recording head.

Hard magnetic material refers to a ferrite material which can retain magnetism for a long time and is not easy to demagnetize after magnetization, also known as permanent magnetic material or permanent magnetic material. The crystal structure of hard magnetic ferrite is roughly hexagonal series of magnetic lead stone, and its typical representative is barium ferrite BaFe12O19. This material has better performance and lower cost, and can be used not only as a magnet for telecommunications devices such as sound recorders, telephones and various instruments, but also in medical, biological and printing display applications.

Magnesium manganese ferrite MG-MnFe3O4, nickel steel ferrite Ni-Cufe2O4 and rare earth pomegranate ferrite 3Me2O3•5Fe2O3 (Me is a trivalent rare earth metal ion, such as Y3+, Sm3+, Gd3+, etc.) are the main magnetic rotation ferrite materials. The rotational magnetism of magnetic materials refers to the phenomenon that the polarization plane of electromagnetic waves constantly rotates around the propagation direction in the process of electromagnetic waves propagating in a certain direction under the action of two mutually perpendicular DC magnetic fields and electromagnetic fields. The phenomenon of magnetic rotation is applied in microwave band. Therefore, magnetic rotation ferrite material is also called microwave ferrite. Mainly used in radar, communication, navigation, telemetry, remote control and other electronic equipment.

The important magnetic moment materials include manganese-zinc ferrite, Li-Ni-Zn ferrite and Li-Mn-Zn ferrite with stable temperature characteristics. Moment magnetic materials have the characteristics of distinguishing physical states, such as "1" and "0" states of electronic computers, "on" and "off" states of various switches and control systems, and "Yes" and "no" states of logical systems. Almost all electronic computers use magnetic ferrite to form high speed memory. Another recently developed magnetic material is the magnetic bubble material. This is because when the magnetic field of some garnet magnetic materials is increased to a certain size, the magnetic domains will form cylindrical bubble domains, which look like bubbles floating on the water surface. The "having" and "nothing" of bubbles can be used to represent the "1" and "0" states of information. By controlling the generation, disappearance, transmission, splitting and interaction of magnetic bubbles by circuits and magnetic fields, the functions of information storage and recording and logical operation can be realized. It has important applications in electronic computers, automatic control and other science and technology.

Magnetostatic material refers to the ferrite material which can be lengthened or shortened mechanically in the direction of magnetic field during magnetization. At present, ni-Zn ferrite, Ni-Cu ferrite and Ni-Mg ferrite are widely used. Magnetopiezoresistive materials are mainly used for the conversion of electromagnetic and mechanical energy into ultrasonic devices, magneto-acoustic devices and telecommunications devices, electronic computers, automatic control devices, etc.