ANOMALOUS PERPENDICULAR MAGNETISM IN NI CU(001) FILMS AND THE EFFECTSOF CAPPING LAYERS/

X-ray magnetic circular dichroism (XMCD) measurements on wedges of Ni grown on Cu(001) are used to investigate magnetic properties in Ni/Cu( 001) ultrathin films. A sharp transition from in-plane to perpendicula r magnetization is found near 7 ML, and a gradual transition back to i n-plane magnetization begins near 37 ML. The critical thickness for ep itaxial growth, 13 ML, is determined from a rapid rise in the coercive field versus film thickness. Both transitions in the direction of eas y axis are well explained by considering the effects of the surface, s hape, and the strain-induced magnetoelastic anisotropies. The critical layer thickness of 13 ML plays a critical role in understanding the t ransition near 37 ML. Capping the Ni wedge with 2 ML of Co increases t he magnitude of the surface anisotropy, forcing the magnetization to r emain in plane for thickness up to at least 18 ML. Addition of an Fe c apping layer has no effect on the direction of magnetization, suggesti ng the importance of interface anisotropies or intermixing. (C) 1996 A merican Institute of Physics.