Hysteretic spin-density-wave ordering in confined geometries

We have measured the antiferromagnetic spin-density-wave (SDW) order in Cr/Cr97.5Mn2.5(001) superlattices. The Mn doping creates a high Neel temperature layer that confines the incommensurate SDW order within the Cr layers. With temperature cycling we observe a transition from commensurate to incommensurate SDW order and discrete changes in the SDW period. We find that these transitions show significant hysteresis (up to 75 K) when the number of SDW nodes within the Cr layer changes by an odd number, while there is no hysteresis for changes of an even number of nodes. This results from the competition between maintaining the spin structure at the interfaces and introducing a spin slip at the nodes of the Cr SDW.