Defect induced magnetism and super spin glass state in reactive ion beam deposited nano-structured AlN thin films

Abstract

Defect induced magnetism is reported in undoped aluminium nitride thin films deposited using reactive ion beam sputtering of aluminium in nitrogen plasma. The films have been deposited on silicon substrate at different temperatures. Existence of the defects in the films has been verified using room temperature photo-luminescence measurements. Owing to nano-crystalline nature of the films, super-magnetic ground states have been observed. A cross-over from super paramagnetic to super spin glass state has been observed as the grain density increases. Detailed magnetisation measurements along with AC susceptibility measurements have been used to determine the ground states in these AlN thin films.