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MA: Magnetismus

MA 12: Oberfl
ächenmagnetismus

MA 12.11: Vortrag

Dienstag, 25. März 2003, 12:45–13:00, HSZ/401

On the origin of the fourth-order magnetic interface anisotropy in epitaxial films — •Günther Bayreuther, Martin Dumm, Brigitte Uhl, Roland Meier, and Wolfgang Kipferl — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg

It was first observed in epitaxial Fe films on Ag(001) and Au(001) that the fourfold in-plane magnetic anisotropy varies with thickness. This is explained by the superposition of a volume term with a positive anisotropy constant (K₁^vol > 0) and a negative interface term (K₁^int < 0) for bcc Fe. This results in an in-plane spin reorientation at a critical thickness of t_crit = 6 ML (monolayers) . To clarify the origin of the interface term, Fe and bcc Fe_1−xCo_x alloy films (x < 0.8) epitaxially grown on different substrates – Ag(001), Au(001), GaAs(001) – were studied. As a result, magneto-elastic interactions can be ruled out because exactly the same anisotropies are found for tensile strain (Fe on Ag(001) and Au(001)) and for compressive strain (Fe on GaAs(001)). A universal correlation is found between the volume and interface anisotropy constants: −K₁^int/K₁^vol = t_crit = 6 ML. Also, K₁^int is the same for Fe/Au and Fe/vacuum interfaces. It is shown that these findings are consistent with Nèel’s phenomenological theory of magnetic anisotropy if contributions from nearest and next nearest neighbors are taken into account. Electronic hybridization effects in this case seem to play a minor role compared to the local symmetry.