Ferrite Cylinder Magnet
The uses and varieties of ferrite magnetic materials have increased with the development of production. According to the application, ferrite can be divided into five categories: soft magnetic, hard magnetic, gyromagnetic, moment magnetic and piezo magnetic.
Ferrite Cylinder Magnet
The uses and varieties of ferrite magnetic materials have increased with the development of production. According to the application, ferrite can be divided into five categories: soft magnetic, hard magnetic, gyromagnetic, moment magnetic and piezo magnetic.
Soft magnetic material refers to a ferrite material that is easy to magnetize and demagnetize under a weak magnetic field (as shown in Figure 1). Typical representatives of soft magnetic materials are manganese zinc ferrite Mn-ZnFe2O4 and nickel zinc ferrite Ni-ZnFe2O4.
Soft magnetic ferrite is a ferrite material with wide application, large quantity, many varieties and high output value among various ferrites. At present, there are dozens of kinds produced in batches in the world, and the annual output has reached more than tens of thousands of tons.
Soft ferrite is mainly used as a variety of inductance components, such as filter cores, transformer cores, antenna cores, deflection cores, magnetic tape recording and video heads, and recording heads for multi-channel communications.
Generally, the crystal structure of soft ferrite is cubic spinel type, which is used in audio frequency to very high frequency band (1 kHz-300 MHz). However, the upper limit of the application frequency of the soft magnetic material with the hexagonal magnetoplumbite crystal structure is several times higher than that of the spinel type.
Hard magnetic materials are relative to soft magnetic materials. It refers to a ferrite material that is not easy to demagnetize after magnetization, but can retain magnetism for a long time. Therefore, it is also sometimes called permanent magnetic material or permanent magnetic material).
The crystal structure of hard magnetic materials is mostly hexagonal magnetoplumbite type. Its typical representative is barium ferrite BaFe12O19 (also known as barium constant porcelain, barium magnetic porcelain), which is a ferrite hard magnetic material with good performance, low cost and suitable for industrial production.
This material can not only be used as a recorder, a microphone, a pickup, a telephone, and a magnet for various instruments in telecommunication devices, but it is also used in pollution treatment, medical biology, and printing displays.
The hard ferrite material is the second main hard magnetic material after the hard magnetic metal materials of the Al-Ni series. Machine components, microwave devices, and other defense devices) open up new avenues for applications.
The gyromagnetism of magnetic materials means that under the action of two mutually perpendicular DC magnetic fields and electromagnetic wave magnetic fields, when a plane-polarized electromagnetic wave propagates in a certain direction inside the material, its polarization plane will continuously rotate around the direction of propagation. Phenomenon, this kind of material with gyromagnetic properties is called gyromagnetic material.
Under the action of DC magnetic field and electromagnetic wave magnetic field, when the plane-polarized electromagnetic wave propagates in a certain direction inside the material, its polarization plane will continuously rotate around the propagation direction. This kind of material with gyromagnetic properties is called gyromagnetic material. Although the metal magnetic H material also has gyromagnetism, due to the small resistivity and too large eddy current loss, the electromagnetic wave cannot penetrate deep into the interior, but can only enter the skin with a thickness of less than 1 micron (also known as the skin effect), so it cannot be used. Therefore, the application of gyromagnetism in magnetic materials has become a unique field of ferrite.
The gyromagnetic phenomenon is actually applied in the band of 100~100,000 MHz (or in the range of meter wave to millimeter wave), so the ferrite gyromagnetic material is also called microwave ferrite. Commonly used microwave ferrites include magnesium manganese ferrite Mg-MnFe2O4, nickel copper ferrite Ni-CuFe2O4, nickel zinc ferrite Ni-ZnFe2O4 and yttrium garnet ferrite 3Me2O3 5Fe2O3 (Me is a trivalent rare earth metal Ions, such as Y3+, Sm3+, Gd3+, Dy3+, etc.)
Most of the gyromagnetic materials are waveguides or transmission lines that transmit microwaves to form various microwave devices, which are mainly used in electronic equipment such as radar, communication, navigation, telemetry, and remote control. Microwave devices are mainly used in electronic equipment such as radar, communication, navigation, telemetry, and remote control.
The moment magnetic material refers to a ferrite material with a rectangular hysteresis loop, as shown in Figure 4. Hysteresis loop means that after the external magnetic field increases to the saturation field strength +Hs, from +Hs to -Hs and then back to +Hs, the magnetic induction of the magnetic material also changes from +Bs to - Bs returns to +Bs again, the closed loop curve experienced. The most commonly used moment magnetic materials are magnesium manganese ferrite Mg-MnFe2O4 and lithium manganese ferrite Li-MnFe2O4.
This kind of material is mainly used as the memory core of various types of electronic computers, and has also been widely used in automatic control, radar navigation, space navigation, information display, etc.
Although there are many new types of memory, magnetic memory (especially magnetic core memory) still occupies a very important position in computing technology due to the abundant raw materials, simple process, stable performance and low cost of ferrite moment magnetic materials.
Piezomagnetic materials refer to ferrite materials that can be mechanically stretched or shortened (magnetostrictive) in the direction of the magnetic field when magnetized. Currently the most widely used are nickel-zinc ferrite Ni-ZnFe2O4, nickel-copper ferrite Ni-CuFe2O4 and nickel-magnesium ferrite Ni-MgFe2O4 and so on.
Piezomagnetic materials are mainly used in ultrasonic and underwater acoustic devices, magneto-acoustic devices, telecommunication devices, underwater TVs, electronic computers and automatic control devices that convert electromagnetic energy and mechanical energy.
Although piezoelectric materials and piezoelectric ceramic materials (such as barium titanate, etc.) have almost the same application fields, they are applied under different conditions due to their different characteristics. It is generally believed that ferrite piezomagnetic materials are only suitable for the frequency band of tens of thousands of hertz, while the applicable frequency band of piezoelectric ceramics is much higher.
In addition to the above classification by use, ferrite can be divided into Ni-Zn, Mn-Zn, Cu-Zn ferrite, etc. according to its chemical composition. Ferrites with the same chemical composition (series) can have various uses. For example, Ni-Zn ferrite can be used as soft magnetic materials, gyromagnetic or piezomagnetic materials, but there are differences in formula and process. Just change.
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