Soft magnetic materials have experienced the development of metal - ferrite - amorphous - nanocrystalline

　　Magnetic material refers to the material with strong magnetism, according to the use can be divided into soft magnetic material, hard magnetic material and functional magnetic material. Soft magnetic material is very easy to magnetize under the action of the magnetic field, and it is easy to demagnetize after eliminating the magnetic field, with high permeability, high saturation magnetic induction strength, small coercivity, small hysteresis loss, used in transformers, relays, inductance core, relays and loudspeaker magnetic conductor, magnetic screen cover, motor stator rotor. And hard magnetic materials are usually difficult to magnetize, difficult to demagnetize, high remanence, high coercivity, mainly used as a magnetic field source for storage and supply of magnetic energy, used in a variety of motors, instruments, equipment, etc.

　　From the perspective of the development history of soft magnetic materials, it has experienced the process of metal soft magnetic materials -- ferrite soft magnetic materials -- amorphous soft magnetic materials -- nanocrystalline soft magnetic materials, and has developed to a more optimized comprehensive performance.

　　Metal soft magnetic: Metal soft magnetic material is a substitute for soft magnetic material, which can be traced back to the mid-19th century. The invention of motor and generator made the metal soft magnetic materials represented by silicon steel develop rapidly. Subsequently, binary system (fe-nickel, fe-aluminum, fe-cobalt, etc.), ternary system (fe-Si-aluminum, fe-cobalt-vanadium, fe-Ni-Mo, etc.) and other multi-alloy soft magnetic materials were introduced successively. The loss of these materials in high frequency application is obviously optimized compared with Fe-Si soft magnetic alloy materials. However, the resistivity of metal soft magnetic materials is generally low, which will produce a large eddy current loss at high frequency. With the increase of the use frequency, its application is gradually limited.

　　Ferrite soft magnetic: In the 1930s, the second generation of soft magnetic materials, ferrite soft magnetic, developed by Snoek of Philip Laboratories in the Netherlands, which has high electrical resistivity and can be used in higher frequency applications than metal soft magnetic. Common soft magnetic ferrites include manganese zinc (MnZn) ferrite, nickel zinc (NiZn) ferrite and magnesium zinc (MgZn) ferrite. Ferrite soft magnetic materials experienced a golden development period from 1950s to 1980s, and are widely used in electronic components such as deflection coils, transformers, inductors and chokes. Gradually in the computer, office automation and other electronic information technology fields and audio-visual equipment, household appliances, green lighting and other terminal industries to achieve rapid penetration. Although the loss of ferrite soft magnetic field is greatly reduced compared with that of metal soft magnetic field in high frequency band, the saturation magnetic induction intensity is significantly lower than that of metal soft magnetic material. In addition, the initial permeability of ferrite soft magnetic field is not high, and its application in the field of low frequency strong electric and high power field with high magnetic energy density is limited.

　　Amorphous soft magnetism: The research and development of amorphous soft magnetic materials began in the 1960s and 1970s. In the 1980s, the Allied Signal Company of the United States built a 7,000-ton amorphous strip production plant, and successively launched a series of amorphous alloy strips named Metglas based on iron (Fe), cobalt (Co) and Fe-Ni. Become an important symbol of the industrialization of amorphous alloys. Amorphous soft magnetic materials are made amorphous by adding glass elements (silicon, boron, carbon, etc.) in the smelting process of some metal soft magnetic (ferromagnetic elements containing iron, nickel, etc.) through fast quenching technology. The saturation magnetic induction strength of amorphous soft magnetic is higher than that of ferrite soft magnetic material, and the resistivity is much higher than that of metal soft magnetic material. The comprehensive performance of amorphous soft magnetic material is better than that of metal soft magnetic material and second generation ferrite soft magnetic material. However, the amorphous soft magnetic properties still have some limitations, such as the initial permeability of iron based amorphous is relatively low, the magnetostrictive coefficient is large, weak field magnetism is poor; The saturation magnetic induction intensity of cobalt-based amorphous is relatively low, which has certain limitations in the miniaturization of magnetic device volume, and high cobalt content leads to high price. Fe-ni - based amorphous Curie temperature is relatively low, the thermal stability is poor.

　　Nanocrystalline soft magnetism: nanocrystalline soft magnetism is a kind of soft magnetic alloy with grain in nanometer level obtained on the basis of amorphous alloy through special heat treatment process. It was developed by Yoshizawa et al., Hitachi Metals in Japan, in 1988. Nanocrystalline soft magnetic field has better comprehensive soft magnetic properties than metal soft magnetic field, ferrite soft magnetic field and amorphous soft magnetic field. Therefore, nanocrystalline soft magnetic field has become an ideal material for high-frequency power electronics applications, and it is also more suitable for the development trend of miniaturization and integration. Taking Antai Technology's nanocrystalline strip as an example, nanocrystalline soft magnetic materials have the following characteristics: 1) high saturation magnetic sensitivity and high permeability: iron based nanocrystalline soft magnetic alloy can have both high saturation magnetic induction intensity (1.25T) and high initial permeability (> 80,000), which is beneficial to the development of iron core to small size and high precision. 2) Low loss: compared with the iron loss of 1/5 of iron based amorphous, the loss is as low as 50W/kg at 100kHz, 300mT, and lower temperature rise; 3) Low coercivity: at static, coercivity is lower than 1.5A/m; 4) Low magnetic extension: close to zero saturation magnetostriction coefficient, so can achieve very low working noise; 5) Excellent temperature stability: in the temperature range of -50℃~150℃ material properties change rate range of ±10%; 6) Excellent frequency characteristics: excellent permeability characteristics and low loss in a wide frequency range; 7) Adjustable magnetic properties: Different types of magnetic properties, such as low remanence type, high rectangular ratio type and high permeability type, can be obtained by applying different strengths of transverse magnetic, longitudinal magnetic or thermal treatment without magnetic field.

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