Dresden 2006 – scientific programme

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MA: Magnetismus

MA 36: Magnetic Coupling Phenomena / Exchange-Bias

MA 36.2: Talk

Friday, March 31, 2006, 11:00–11:15, HSZ 401

Asymmetry and time dependent effects in IrMn exchange biased bilayers — •Christine Hamann¹, Jeffrey McCord¹, Dieter Elefant¹, Rudolf Schäfer¹, Ludwig Schultz¹, and Roland Mattheis² — ¹Leibniz Institute for Solid State an Materials Research Dresden, Helmholtzstraße 20, 01069 Dresden — ²Institute for Physical High Technology Jena, Albert - Einstein - Str. 9, 07745 Jena

Measurements by inductive and spatially resolved magnetooptical magnetometry revealed an asymmetric magnetization reversal of both Co₉₀Fe₁₀(20nm) and Ni₈₁Fe₁₉(20nm)/Ir₂₃Mn₇₇ bilayers. For varying Ir₂₃Mn₇₇ thicknesses (2.5-10nm) different extents of misalignment of the effective easy magnetization axis have been detected. The misalignment of the effective easy axis strongly influences the hysteresis shape and thereby the asymmetry. In addition, a corresponding asymmetry in domain nuclation and formation is found. Moreover, a major influence on the asymmetry results from irreversible and time dependent switching processes by the antiferromagnet. Measurements by means of magnetooptical and alternating gradient magnetometry (AGM) have been performed to investigate that particular contribution in more detail. The results show that both the degree of asymmetry and the effective exchange bias field can be modified by a static magnetic field as well as the measuring frequency. This observed training effect is dicussed in terms of irreversible contributions of the antiferromagnet in the sense of a rotatable anisotropy.