Magnetic properties of amorphous ferromagnets (invited)

摘要

Some magnetic properties of amorphous ferromagnets are well described within the randomhyphen;anisotropy realhyphen;space model. This model assumes that the neighboring spins are ferromagnetically coupled with each other, and that there is a local magnetic anisotropy whose axes are correlated over a small lengthRadue to shorthyphen;range structural order. The system is characterized by a small parameter lgr;sim;R2aK/Awhich depends on temperature and on the concentration of magnetic atoms via the local anisotropyKand exchange constantA. In zero magnetic field the local magnetization smoothly rotates over the solid with a characteristic lengthRf=Ra/lgr;2. The zerohyphen;field susceptibility is very sensitive to the exchange, the anisotropy, and the amorphous structure: khgr;prop;A3Kminus;4Rminus;6a. The magnetization law in approaching saturation (Mrarr;M0) is universal (M0minus;M)prop;1/(H)1/2forH2A/M0R2a. These and other predictions of the model seem to be in a good agreement with many recent experimental results.