Sputtering-induced recrystallization on the target and its effect on magnetic properties of amorphous rare-earth transition metal thin films

Abstract

An investigation was made to evaluate the variation in the magnetic hysteretic properties of rf-sputtered amorphous Tb-Fe thin films as a function of sputtering parameters, such as Ar pressure and rf input power. It was discovered that, during sputtering from a composite target which consists of rare-earth disks placed on a transition metal plate, the average surface composition of the target changed by formation of intermetallic RE-TM compounds through a recrystallization process on the RE disk surface. Using x-ray diffraction, electron microprobe, and scanning electron microscopy, analysis of the surface revealed that the amount and morphology of intermetallic compounds formed had a strong dependence on Ar pressure but a lesser dependence on power. The magnetic properties of the films deposited under different sputtering conditions were measured using Kerr magneto-optic and VSM hysteresis loop tracers. The results show that the changes in the magnitude of magnetization, coercivity, and polarity of the hysteresis loop of the films obtained from a given sputtering target with various sputtering parameters are the consequence of changes in film composition which arise from the altered surface composition and morphology of the sputtering target.