| Magneto-optical recording is realized by using thermomagnetism to record information and Kerr effect to readout information. Magneto-optical disc has advantages of high storage density, non-volatilization, high stability and long storage life. With the development of magneto-optical material theory and material preparing methods, it's of great important to research the measurement methods of magneto-optical characteristics. The research of this dissertation includes: a new method of Kerr effect measurement was presented through theoretical analysis; magneto-optical characteristic measuring system was developed; many studies on Kerr rotation angle measuring circuit, light path and error analysis of system were done as well.Simple mathematic relation between Kerr rotation angle, reflectivity and linear light intensity out from a Polarizing Beam Splitter was deduced by phenomenological theory of magneto-optical effect, which made it possible that Kerr rotation, reflectivity could be obtained through simple analog circuit.Kerr rotation angle measuring circuit consists of signal acquisition, data processing, display, result output and power supply. The technologies of light-to-current conversion, difference amplifier and filtering were used; the problem of weak signal detection was solved; various noises were decreased or restrained effectively. Special reflector and bracket were designed and proper calibrating step was adopted to ensure the light path work steadily and accurately.In addition, noise of the system was analyzed and calculated, static characteristics were determined by error analysis.The measuring system has been used to obtain the magneto-optical characteristic of commercial MO disc, series of TbFeCo and Nd(Tb,Dy)Co MO thin films successfully. The range and precision of measuring system were satisfactory for scientific research and teaching experiments. |
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