Magnetic thermal hysteresis inFem∕Dyn∕FemandGdm∕Dyn∕Gdmtrilayers

We have performed a theoretical investigation of thermal hysteresis in the magnetization of ${\mathrm{Fe}}_{m}∕{\mathrm{Dy}}_{n}∕{\mathrm{Fe}}_{m}$ and ${\mathrm{Gd}}_{m}∕{\mathrm{Dy}}_{n}∕{\mathrm{Gd}}_{m}$ trilayers, where the interface coupling is antiferromagnetic and ferromagnetic, respectively. Our results show a large number of stable states can exist in these structures. The thermal hysteresis occurs because the transitions between these states occur at different temperatures for the heating and cooling processes. The thermal hysteresis can be quite large, spanning about $90\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Furthermore the temperature span of the thermal hysteresis can be substantially reduced by applying a modest external magnetic field.