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 investigated by means of the sample-tilting X-ray diffraction (STD), optical absorption spectroscopy, Mossbauer spectroscopy and saturation magnetization measurement. The analysis results indicate that there exist a critical dose 1.0 X 10(14) ions/cm(2) and a threshold value of electronic energy loss S-e = 2.9 MeV/mu m. Above both values the lattice constant a, the optical absorption coefficient alpha, and the fraction of the paramagnetic phase F-p increase with the increase of electronic energy 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). It is found that the transformation from crystalline to amorphous state is a gradual process in which the electronic stopping power plays a main role and a certain dose is needed.