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

TL;DR

This study reports defect-induced magnetism and a transition from superparamagnetic to super spin glass states in nano-structured AlN thin films deposited by reactive ion beam sputtering, with properties verified through various magnetic and luminescence measurements.

Contribution

It demonstrates the emergence of magnetic states in undoped AlN films due to defects and reveals a transition from superparamagnetism to super spin glass behavior related to grain density.

Findings

Defect-induced magnetism confirmed via photoluminescence.

Observation of super-magnetic ground states in nano crystalline AlN.

Transition from super paramagnetic to super spin glass state with increasing grain density.

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 have 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.