Types and uses of ferrite 2

4. Moment Ferrite

The rectangular ferrite is a ferrite with a rectangular hysteresis loop and a large coercive force. This material is widely used in cutting-edge science and technology such as electronic computers, automatic control and remote control, and is used to make memory elements, switching elements and logic elements, magnetic amplifiers, magneto-optical memories and magnetic memories. Rectangular magnetic materials are mainly used to make toroidal cores in magnetic memory, and until now it is still the most used element in internal memory. With the development of electronic computers in the direction of high-speed and large-capacity, the size of the ring-shaped ceramic core is increasingly miniaturized, and the diameter has been reduced from the original 0.75mm to 0.5~0.3mm, and it is still trying to reduce it. It has the advantages of high resistivity, strong radiation resistance, high reliability, and low cost. Generally, spinel-type ferrites with high density, uniform crystal grains and large crystal anisotropy are made of good magnetic properties. Moment magnetic material. The rectangular ferrite materials at room temperature include Mn-Mg series, Cu-Mn series, and Gd-Mn series; the wide temperature moment magnetic materials in the temperature range of -65~+125℃ include Li series, Ni series, etc. At present, the large-scale rectangular ferrite materials mainly include Mn-Mg series and Li series.

5.Magnetic bubble material

Magnetic bubble material is a new type of magnetic storage material with great application prospects. The so-called magnetic bubble is a circular magnetic domain in ferrite.

When the films and diaphragms of some garnet-type materials have a single magnetization axis that realigns the film surface, under the action of a certain external magnetic field, it is possible to produce cylindrical magnetic domains on the film surface. It looks like a bubble in the direction of the film surface, so it is vividly called a magnetic bubble.

The key to the magnetic bubble device is the material. The material that can produce magnetic bubbles is the perovskite type rare earth orthoferrite single crystal HoFeO3,

ErFeO3, TmFeO3, YbFeO3, LuFeO3, NdFeO3, etc. However, the bubble diameter of this material is too large and the temperature stability is also poor.

Later, garnet-type ferrite and amorphous magnetic bubble materials (such as Gd-Co, Gd-Fe film) were developed, among which garnet-type oxygen body has a small bubble diameter and high mobility, which is a practical magnetic bubble material. This magnetic bubble material is made of non-magnetic gadolinium gallium garnet is used as the substrate to epitaxially grow rare earth-containing garnet films that can generate magnetic bubbles. Through the adjustment of the composition, the characteristics such as the bubble diameter and mobility of the magnetic bubble can be changed.

6. Magneto-optical materials

Magneto-optical materials are mainly used to manufacture external storage of large-scale electronic computers-magneto-optical memory. This kind of memory has the storage density is 100~1000 times higher than the general drum and disk storage.

Magneto-optical memory is a kind of magnetic device that uses magneto-optical effect to store magnetic materials. The so-called magneto-optical effect is a partial table.

After the light is reflected or transmitted by the magnetic medium, its polarization state changes and the polarization plane rotates. Backup due to reflection the rotation of the plane is called the Kerr effect, and the rotation of the plane of polarization caused by transmission is called the Faraday effect.

The basic requirements of magneto-optical materials are good light transmittance, certain magnetization strength and coercoerity, and appropriate transition temperature, etc. In addition to the more studied crystalline and amorphous alloy film, there are yttrium iron garnet ferrite single crystal, rare earth europium oxide EUO and Eu sulfur compounds.

7. Piezo Ferrite

On magnetostrictive effect for the application of the principle of ferrite magnetic ferrite is called pressure Often like this kind of material with high magnetostrictive effect Magnetostrictive effect refers to the magnetic materials in the process of magnetization, geometry size and shape change phenomenon Describe the parameters of the effect size for line magnetostrictive coefficient, often said by length and relative changes.

Magnetostrictive ferrite is mainly used in ultrasonic devices (such as ultrasonic flaw detector, ultrasonic drill, ultrasonic welder, etc.), underwater acoustic devices (such as sonar echo detector, mechanical filter, mixer, pressure sensor and ultrasonic delay line, etc. Its advantages are high resistivity, good frequency response and high electroacoustic efficiency.

Piezo Ferrite

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