Metastable magnetism and memory effects in dilute magnetic semiconductors

Detailed magnetic measurements on the dilute magnetic semiconductors (DMS) Cr and Gd are carried out. These two materials have previously been reported to exhibit room temperature magnetic order. We show that the existence of magnetic hysteresis cannot be taken as proof for conventional ferromagnetism. Instead, we find an unparalleled metastable magnetic behavior together with memory effects in both materials, suggesting that for most DMS metastability plays a crucial role in accounting for the magnetic order even at elevated temperatures up to 400K. © 2008 IOP Publishing Ltd.