Magnetism of chromium at surfaces, at interfaces and in thin films

The spin density wave (SDW) magnetism of thin epitaxial Cr films has recent ly become the focus of interest because of its mediating role in exchange c oupled superlattices. While the incommensurate SDW magnetism and the Neel t emperature are well established for bulk Cr, the question arises of how the se properties are altered in thin films and superlattices either due to dim ensionality effects or due to proximity with the ferromagnetic or paramagne tic boundary layers. After a brief introduction to the basic properties of bulk Cr, this review provides an overview of the SDW magnetism in thin Cr f ilms, starting with surface properties and continuing with the discussion o f Cr films of various thickness. The emphasis is more on SDW order in diffe rent confined environments than on exchange coupling. The scaling of the Ne el temperature with thickness, the critical thickness for the onset of SDW order, the orientation of the SDW wave vector in different environments and the enhancement of SDW order due to proximity effects are extensively disc ussed. Most important is the role of the interface roughness in case of con tact with a ferromagnetic layer. Conflicting results obtained with differen t experimental techniques are critically reviewed and an interpretation of the SDW order depending on interface quality is proposed.