1 GEV AR IONS INDUCED AMORPHIZATION IN GARNET

Amorphization phenomenon of yttrium iron garnet (YIG) Y3Fe5O12 induced by 1 GeV Ar ions irradiation at the temperature 195 K has been invest igated by means of the sample-tilting X-ray diffraction (STD), optical absorption spectroscopy, Mossbauer spectroscopy and saturation magnet ization measurement. The analysis results indicate that there exist a critical dose 1.0 X 10(14) ions/cm(2) and a threshold value of electro nic energy loss S-e = 2.9 MeV/mu m. Above both values the lattice cons tant a, the optical absorption coefficient alpha, and the fraction of the paramagnetic phase F-p increase with the increase of electronic en ergy loss, but saturation magnetization decreases, For the first time, the nearly complete amorphous state was observed at S-e = 8.3 MeV mu m with irradiation doses equal or more than 1.0 X 10(14) ions/cm(2). I t is found that the transformation from crystalline to amorphous state is a gradual process in which the electronic stopping power plays a m ain role and a certain dose is needed.