Magnetization reorientation in Ni (111) ultrathin flms studied by low-temperature hysteresis measurements

Surface magneto-optical Kerr e!ect (SMOKE) magnetometry in the temperature range 10}300 K was exploited to investigate the magnetic properties of high-quality Cu/Ni/Cu/Si(1 1 1) epitaxial heterostructures with thickness of the Ni layer, dN*, between 10 and 60 As . For a "xed temperature, the equilibrium direction of the magnetization is parallel or perpendicular to the "lm surface, depending on the Ni thickness, because of the competition among shape anisotropy, magnetoelastic anisotropy and interface anisotropy. No reorientation of the magnetization could be observed as a function of temperature, for any of the specimens analyzed, while a large variation of the loop squareness and coercivity was found. This last variation has been qualitatively explained using a theoretical model based on a Green's function technique, valid for a monodomain "lm with a coherent rotation of the magnetization. ( 2000 Elsevier Science B.V. All rights reserved.