Dresden 2006 – scientific programme

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MA: Magnetismus

MA 14: Magnetic Thin Films II

MA 14.11: Talk

Tuesday, March 28, 2006, 12:45–13:00, HSZ 03

Perpendicular magnetic anisotropy induced by tetragonal distortion of FeCo alloy films grown on Pd(001) — •Aimo Winkelmann, Marek Przybylski, Feng Luo, Yisheng Shi, Jochen Barthel, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany

We grew tetragonally distorted Fe_xCo_1−x alloy films on Pd(001). The films were grown at 295 K by molecular beam epitaxy using thermal evaporation from two effusion cells. Theoretical first-principles calculations for such films predict a high saturation magnetization and a high uniaxial magnetic anisotropy energy for specific values of the lattice distortion c/a and the alloy composition x. The magnetic anisotropy was investigated using the magneto-optical Kerr effect. For films of varying composition, we observed a spin-reorientation transition from in-plane to out-of-plane and back to in-plane with increasing cobalt content. Out-of-plane anisotropy was observed for Fe_0.5Co_0.5 films in the thickness range of 4 to 14 ML. Using low energy electron diffraction Kikuchi patterns, the c/a value of about 1.13±0.02 obtained for the tetragonal distortion is consistent with the results formerly obtained for pure Fe (1.11) and Co (1.15) films on Pd(001). The magnetic anisotropy energy induced by the tetragonal distortion is estimated to be almost two orders of magnitude larger than the value for bulk FeCo alloys. A decrease of the tetragonal distortion with thickness can be related to a decrease of the out-of-plane anisotropy energy which is overturned by the in-plane magnetostatic energy above the thickness of 14 ML.