Spin-density waves and reorientation effects in thin epitaxial Cr films covered with ferromagnetic and paramagnetic layers

We report about synchrotron and neutron-scattering studies investigating in commensurate spin-density waves (I-SDW's) in epitaxially grown thin Cr(001) films, including surface and interface effects. These studies show that th in ferromagnetic cap layers of Fe, Ni, and Co with a thickness of only 2-3 nm have a strong effect on the propagation and orientation of the I-SDW's i n Cr. For thick Cr films there exist essentially only transverse I-SDW's pr opagating parallel to the:film plane with the spins oriented normal to the planet and at right angles to the in-plane magnetization of the ferromagnet ic cap layers. With decreasing Cr thickness a different transverse I-SDW gr ows at the expense of the in-plane ones, now propagating normal to the plan e and with spins parallel or antiparallel to the film magnetization. At a C r thickness of about 250 Angstrom, the transverse out-of-plane I-SDW comple tely dominates the phase diagram of Cr. All other domains are suppressed an d a spin-flip transition does not occur above 10 K in strong contrast to bu lk. For in-plane propagation of the T-SDW we find a coexisting commensurate spin-density wave (C-SDW) which vanishes during the reorientation to. out- of-plane propagation with Cr thickness. Finally,for Cr thicknesses well bel ow the period of the I-SDW, the Cr can only order as a C-SDW. The behavior of the SDW's in thin Cr films with ferromagnetic cap layers can be understo od in terms of competing interactions at the rough interfaces inducing frus tration and by finite-size and strain effects. We have also investigated th e effect of Cu and Pd cap layers on the SDW. The Cu cover is similar to a C r/vacuum interface, whereas the effect of the Pd cover is intermediate betw een the ferromagnetic layers and Cu. [S0163-1829(99)11513-3].