Phase-change magnetic memory effect in cation-deficient iron sulfide Fe1−xS

We report the discovery of magnetic memory effect in cation-deficient iron sulfide Fe1−xS. This nonstoichiometric sulfide shows a transition from a ferrimagnet to an antiferromagnet induced by an order-disorder transition of cation defects. The magnetic properties of Fe0.92S, at the critical composition for the order-disorder transition, were reliably controlled by the use of appropriate heat treatments; the slow-cooled sample showed ferrimagnetism with a spontaneous magnetization, while the quenched samples displayed superparamagnetic behavior without hysteresis. We propose that this material can be used as part of a nonvolatile phase-change memory device.