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MA: Fachverband Magnetismus

MA 26: Exchange Bias

MA 26.6: Vortrag

Donnerstag, 29. März 2007, 16:30–16:45, H10

Analysis of effective magnetic anisotropies in exchange-coupled bilayer systems — •Daniel Markó^1,2, Jeffrey McCord², Rudolf Schäfer², Rainer Kaltofen², and Ludwig Schultz² — ¹Forschungszentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 128, D-01328 Dresden — ²Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Helmholtzstraße 20, D-01069 Dresden

We have investigated the effective magnetic anisotropies in FM/AFM exchange-coupled Ni₈₁Fe₁₉/Ir₁₉Mn₈₁ bilayers with constant FM and varying AFM layer thickness. The samples have been prepared by either RF or DC magnetron sputtering to study the effect of different AFM grain sizes. In addition, the influence of thermally activated processes in the AFM layer has been investigated by annealing the samples with varying temperature, durations, and cooling rates. By using two magnetometric methods with different experimental time scales, a separation of different anisotropy contributions was possible. Quasistatic measurements yield the coercivity H_C and the exchange-bias field H_eb,ea. From the dynamic experiment the exchange-bias field H_eb,dyn, the rotatable anisotropy H_rot, the ferromagnetic resonance frequency f_res, and the effective magnetic damping parameter α were determined. Moreover, magnetization processes have been observed by means of Kerr microscopy. Our experimental results were compared with models for exchange-bias and are in agreement with the models of Malozemoff, Fulcomer and Charap, and McMichael and Stiles.