DEPTH-DEPENDENT INVESTIGATION OF THE DISTRIBUTION OF THE SPIN-DENSITYWAVES IN THIN CHROMIUM FILMS WITH SURFACE X-RAY AND NEUTRON-SCATTERING

For thin epitaxial Cr(001) films capped with a ferromagnetic Fe layer a transverse spin density wave (SDW) is expected which propagates in t he out-of-plane direction with the Cr spins aligned parallel to the fi lm plane in the direction of the Fe magnetization vector. Synchrotron and neutron scattering experiments show, however, that the SDW wave pr opagates parallel to the film plane with spins oriented out-of-plane. In addition, a commensurate antiferromagnetic phase is found. The re-o rientation of the SDW is caused by a frustrated Fe-Cr exchange couplin g introduced by monoatomic steps at the Fe-Cr interface. Complete re-o rientation takes place over some distance close to the interface reduc ing severely the coherence length of the SDW structure. With the surfa ce scattering method we have measured the coherence length of the SDW as a function of depth. Furthermore, we have investigated the role of the commensurate antiferromagnetic phase near the Fe-Cr interface. We find no scattering from a commensurate order, implying a layering of t he two phases with the incommensurate phase on top. (C) 1998 Elsevier Science B.V. All rights reserved.