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Rare earth magneto optical material

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Update time : 2018-01-05 16:38:07

Rare earth magneto optical material

一、Rare earth magneto optical material
Under the effect of magnetic field or a magnetic moment, the electromagnetic properties of the material (such as magnetic conductivity, dielectric constant, the intensity of magnetization, the magnetic domain structure, the magnetization direction, etc.) will change.So that leads to the transmission characteristics of light material also will change.Light lead to the material under the action of magnetic field or a magnetic moment, the change of its transmission characteristics are called magneto-optic effect.

Magneto-optic material refers to the ultraviolet to infrared wavelengths, with magneto-optic effect of optical information function materials.Using the magneto optical property of this kind of material as well as light, electricity, magnetic interaction and conversion, can be made into optical device with a variety of functions, such as modulator, isolator, circulator, switch, deflector, optical information processor, display, storage, laser gyro partial frequency magnetic mirror, magnetometer, magneto optical sensors, printing machine, etc.

Rare earth elements because of 4 f electronic shell with vacancy, thus produce: not offset magnetic moment, this is the source of the strong magnetic, as a result of 4 f electronic transition, this is the cause of the excitation light, resulting in strong magneto-optic effect.Pure rare earth metal effect, does not appear, this is because the rare earth metals has not been preparation into optical material.Only when the rare earth element doped compounds optical glass, crystal, alloy thin film optical materials, such as to emerge strong magneto-optic effect of rare earth elements.


二、the application of rare earth magneto-optical materials
Magneto-optical devices refers to the use of magneto-optical effects of materials made of various types of optical information functional devices. Although Faraday discovered the magneto-optical effect in 1845, it was not applied for the next more than 100 years. Until the early 60, due to the development of laser and photoelectron technology, the study of magneto-optical effect to the field of application, the emergence of a new type of optical signal functional devices-magneto-optical devices.

In laser applications, in addition to exploring a variety of new lasers and receivers, laser beam parameters, such as strength, direction, deflection, frequency, polarization state, such as rapid control is also very important problem, magneto-optical devices, is the use of magneto-optical effect of a variety of laser beam control devices, similar to the development of microwave ferrite devices and classification, Due to the need of optical communication, the 1966 has developed magneto-optical modulator, magneto-optical switch, magneto-optical isolator, magnetic ring Line, magneto-optical rotary, magneto-optical phase shifter and other magneto-optical devices.

Due to the development of optical fiber technology and integrated optics, the integrated magneto-optical device of waveguide type was born in 1972. In the late 60, magneto-optical storage technology was developed because of the development of computer storage technology. Later, due to the perfect and commercialization of holographic magnetic bubbles and optical disc technology, magneto-optical printing and magneto-optical disc system appeared. Magnetic bubble technology is developed by using magneto-optical effect to study cylindrical magnetic domain (magneto-bubble).

Due to the need of information technology, in the late 70, on the basis of magnetic bubble technology, the development of magneto-optical information processing machine and magnetic bubble display. In the development of laser gyro, the problem of "latching" has been encountered, and it has been frustrated, and then the magneto-optical effect has been successfully used to overcome the "latching", thus developing a magneto-optical bias laser gyro with solid state (without mechanical components). Therefore, each new type of magneto-optical devices are developed successfully on the basis of studying magneto-optical effect.


1. Magneto-Optical modulator
The magneto-optical modulator uses polarized light to modulate the beam by rotating the polarization surface through the magneto-optical medium. Magneto-optical modulator has a wide range of applications, can be used as a chopper of infrared detectors, can be made into infrared radiation pyrometer, high sensitivity polarization meter, but also for the display of television signal transmission, ranging devices and a variety of optical detection and transmission systems.

2. Magneto-optical sensor
A device that detects a magnetic field or current by magneto-optical effect is called a magneto-optical sensor. It integrates laser, optical fiber and optical technology in one, the optical way to detect the strength and state of the magnetic field and current changes, can be used for high-voltage network detection and monitoring, but also for precision measurement and remote control, telemetry and automatic control system.

3. Magneto-Optical Isolator
In optical fiber communication, optical information processing and a variety of measurement systems, there is a need for a stable light source, because the system in the connection of different devices tend to reflect a part of the light, once these reflected light into the laser source cavity, will make the laser output instability, thus affecting the entire system's normal work. Magneto-Optical isolator is a kind of magneto-optical non-reciprocity device which is developed to solve this problem. It can make the forward transmission of light through the barrier, and all exclude from the optical fiber functional device points reflected back from the light, thereby effectively eliminating the laser source noise.

4. Magneto-Optical recording
Magneto-optical record is the rapid development of the recent more than 10 years of High-tech. Magneto-Optical recording is currently the most advanced information storage technology, it has both disk and optical advantages. Magnetic discs are widely used in national management, military, public security, aerospace, astronomy, meteorology, hydrology, geology, petroleum minerals, posts and telecommunications, transportation, statistical planning, such as the need for large-scale data real-time collection, recording, storage and analysis, especially for the collection of sound, image, communication, data calculation, analysis, The functions of the magneto-optical storage system cannot be replaced by other storage methods for multimedia computers.

Magneto-optical storage is a magnetic domain which is perpendicular to the film surface by laser heating and applying the revers e magnetic field on the rare earth amorphous alloy film, and the magnetic domain is used to write the information, and the Kerr magneto-optical effect is used to read it.

Magnetic disc is the beginning of the 80 's application of the product, CD-ROM there are three major categories. One is read-only, the recorded signal on the disk can not erase, can not be rewritten, can only read, like "Record", the current market of VCD disc is. The second type is a write-type, the original CD-ROM, like a blank "tape" can input information and read out, but once the input information can no longer erase.

The third category is Erasable, which, like a disk, can be erased, rewritten, and read out. Because of its writing, reading through the material magneto-optical effect, and disk without mechanical contact, so long life, repeated wipe, write up to millions (life expectancy more than 10 years, and the general CD-ROM is about 2 years). Moreover, the magnetic disc recording density is 50 times times the hard disk, it is the 800~1000 times of ordinary PC floppy disks, so it develops very quickly.

The magneto-optical disc is a recording medium of amorphous alloy films of rare earth Elements (RE), Dysprosium, gadolinium, and Transition Group metal (TM) iron and cobalt. This magneto-optical recording film is deposited by vacuum sputtering with Tb-feco and other RE-TM alloy targets, and RE-TM alloy target is the key material for manufacturing magnetic discs.

Japan and other developed countries in 1988 to the magnetic disc system to market, it is reported that in 2000 only Japan's magnetic disc system market will reach 1 trillion yen.