Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 26: Exchange Bias

MA 26.11: Vortrag

Donnerstag, 29. März 2007, 17:45–18:00, H10

Effects of nonmagnetic dilutions in metallic antiferromagnets on exchange bias — •Marian Fecioru-Morariu¹, Syed Rizwan Ali¹, Cristian Papusoi², Martin Sperlich¹, and Gernot Güntherodt¹ — ¹Physikalisches Institut (IIA), RWTH Aachen, 52056 Aachen, Germany — ²SPINTEC, CEA/CNRS, 38054 Grenoble Cedex 9, France

The effects of dilution of metallic antiferromagnets by nonmagnetic elements on the exchange bias are investigated in bilayers of Co₇₀ Fe₃₀ / (Ir₂₂ Mn₇₈)_1−x Cu_x from a structural, magnetic and Monte Carlo simulation point of view. The nonmagnetic dilution by Cu throughout the volume of the antiferromagnet (AFM) Ir₂₂Mn₇₈ gives rise to an enhanced exchange bias field (H_EB). At the same time, lattice matched Cu dilutions give rise to a reduction of the AFM grain size and hence of the blocking temperature (T_B). The enhancement and maximum of H_EB as a function of Cu dilution is found to result from the competition of the increased number of uncompensated AFM moments and the reduction of T_B. The thermoremanent magnetization (M_TRM) of the diluted AFM-only, is also enhanced and decreases with increasing temperature in qualitative agreement with H_EB. This indicates the underlying close connection between H_EB of the FM/AFM bilayer and M_TRM of the AFM only. Our experimental results are in very good agreement with Monte Carlo simulations based on a Heisenberg model. The financial support through the EU Research Training Network NEXBIAS (Contract No. HPRN-CT-2002-00296) is gratefully acknowledged.