What is magnetic material - Solutions - Huaqiang Electronic Network

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1. Magnetization curve of magnetic material Magnetic material is composed of ferromagnetic substance or ferrimagnetic substance. Under the action of external magnetic field H, there must be corresponding magnetization M or magnetic induction intensity B, which are called with the curve of magnetic field strength H. It is a magnetization curve (M~H or B~H curve). The magnetization curve is generally non-linear and has two characteristics: magnetic saturation and hysteresis. That is, when the magnetic field strength H is sufficiently large, the magnetization M reaches a certain saturation value Ms, and continues to increase H, Ms remains unchanged; and when the M value of the material reaches saturation, the external magnetic field H decreases to zero, M Does not return to zero, but changes along the MsMr curve. The working state of the material is equivalent to a point on the M to H curve or the B to H curve, which is often referred to as the working point.
2. Common magnetic properties of soft magnetic materials Saturation magnetic induction Bs: The size depends on the composition of the material, and its corresponding physical state is that the magnetization vectors inside the material are neatly arranged.
The residual magnetic induction Br: is the characteristic parameter on the hysteresis loop, and the B value when H returns to zero.
Rectangular ratio: Br∕Bs
The coercive force Hc: is an amount indicating the degree of difficulty in magnetization of the material, and depends on the composition and defects (impurities, stress, etc.) of the material.
Permeability μ: is the ratio of B to H at any point on the hysteresis loop, which is closely related to the operating state of the device.
Initial magnetic permeability μi, maximum magnetic permeability μm, differential magnetic permeability μd, amplitude magnetic permeability μa, effective magnetic permeability μe, and pulse magnetic permeability μp.
Curie temperature Tc: The magnetization of ferromagnetic material decreases with increasing temperature. When a certain temperature is reached, the spontaneous magnetization disappears and becomes paramagnetic. The critical temperature is the Curie temperature. It determines the upper limit temperature at which the magnetic device operates.
Loss P: hysteresis loss Ph and eddy current loss Pe P = Ph + Pe = af + bf2+ c Pe ∝ f2 t2 / , ρ decreases,
The method of hysteresis loss Ph is to lower the coercive force Hc; the method of reducing the eddy current loss Pe is to thin the thickness t of the magnetic material and increase the resistivity ρ of the material. The relationship between the loss of the core and the temperature rise of the core in free still air is:
Total power dissipation (mW) / surface area (cm2)
3. Conversion between the magnetic parameters of the soft magnetic material and the electrical parameters of the device When designing the soft magnetic device, the voltage-current characteristics of the device must first be determined according to the requirements of the circuit. The voltage-to-current characteristics of the device are closely related to the geometry and magnetization state of the core. The designer must be familiar with the magnetization process of the material and grasp the conversion relationship between the magnetic parameters of the material and the electrical parameters of the device. Designing a soft magnetic device usually involves three steps: correct selection of magnetic material; reasonable determination of the geometry and size of the magnetic core; according to the magnetic parameters, the working state of the simulated magnetic core obtains corresponding electrical parameters.
Magnetic materials are an important electronic material. Early magnetic materials mainly used metal and alloy systems. With the development of production, high-performance magnetic materials with high electrical resistivity are urgently required in the power industry, telecommunications engineering and high-frequency radio technology. On the basis of re-examining magnetite and other magnetic oxides, a new magnetic material, ferrite, was developed. Ferrite is a magnetic material of an oxide system, and is a composite oxide mainly composed of iron oxide and other iron group elements or rare earth element oxides, and can be used for various functional devices for energy conversion, transmission, and information storage.
Ferrite magnetic materials can be classified into spinel type (MFe2O4), garnet type (R3Fe5O12), magnetoplumbite type (MFe12O19), and perovskite type (MFeO3) according to their crystal structure. Wherein M is a divalent metal ion having an ionic 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 magnetic, hard magnetic, rectangular magnetic and piezoelectric magnetic.
A soft magnetic material is a ferrite material that is easily magnetized and demagnetized under a weak magnetic field. The soft ferrites with practical value are mainly MnZn ferrite Mn-ZnFe2O4 and nickel zinc ferrite Ni-ZnFeO4. The crystal structure of the soft ferrite is generally a cubic crystal spinel type, which is a kind of material which is widely used in various ferrites, has a large number, a large variety, and a high output value. It is mainly used as a magnetic head for magnetic and tape recording and recording of various inductance components such as filters, transformers and antennas.
A hard magnetic material is a ferrite material that is not easily demagnetized after magnetization and can retain magnetism for a long period of time, and is also called a permanent magnet material or a constant magnetic material. The crystal structure of the hard ferrite is roughly a hexagonal magnetite type, which is typically represented by barium ferrite BaFe12O19. This material has better performance and lower cost, and can be used not only as a magnet for telecommunication devices such as sound recorders, telephones, and various instruments, but also for medical, biological, and printed displays.
Magnesium-manganese ferrite Mg-MnFe3O4, nickel-steel oxide Ni-CuFe2O4 and rare earth pomegranate ferrite 3Me2O3•5Fe2O3 (Me is a trivalent rare earth metal ion such as Y3+, Sm3+, Gd3+, etc.) is the main gyromagnetic body material. The gyromagnetic material of a magnetic material refers to the phenomenon that the polarization plane will continuously rotate around the propagation direction during the propagation of electromagnetic waves in a certain direction inside the material under the action of two mutually perpendicular DC magnetic fields and electromagnetic wave magnetic fields. The gyromagnetic phenomenon is actually applied in the microwave band, and therefore, the gyromagnetic material is also called microwave ferrite. Mainly used in radar, communication, navigation, telemetry, remote control and other electronic equipment.
Important momentary magnetic materials are MnZn ferrite and Li-Ni-Zn ferrite and Li-Mn-Zn ferrite with stable temperature characteristics. The magnetic material of the moment has the characteristics of distinguishing the physical state, such as the "1" and "0" states of the electronic computer, the "on" and "off" states of the various switches and control systems, and the "yes" of the logic system and "No" two states, etc. Almost all electronic computers use a rectangular ferrite to form a high speed memory. Another newly developed magnetic material is a magnetic bubble material. This is because when a certain garnet-type magnetic material film is applied to a certain magnetic field, the magnetic domain forms a cylindrical bubble domain, which looks like a blisters floating on the water surface. The "yes" and "none" of the bubble can be used to represent The "1" and "0" status of the message. The circuit and the magnetic field control the generation, disappearance, transmission, splitting and interaction of the magnetic bubbles, so that the information storage and logic operations can be realized. It is important in the science and technology of electronic computers and automatic control. application.
A piezoelectric material refers to a ferrite material that can be mechanically elongated or shortened in the direction of a magnetic field when magnetized. At present, nickel-zinc ferrite, nickel-copper ferrite and nickel-magnesium ferrite are the most widely used. The piezoelectric material is mainly used for ultrasonic devices, magneto-acoustic devices and telecommunication devices, electronic computers, automatic control devices, etc., in which electromagnetic energy and mechanical energy are mutually converted.