Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 19: Micro Magnetism / Computational Magnetism
MA 19.4: Vortrag
Mittwoch, 25. März 2009, 11:00–11:15, HSZ 403
IrMn: the role of the anisotropy for exchange bias — •Jerome Jackson1, Ulrich Nowak1, Laszlo Szunyogh2, Bence Lazarovits2,3, and Laszlo Udvardi2 — 1Fachbereich Physik, Universität Konstanz, Germany — 2Department of Theoretical Physics, Budapest University of Technology and Economics, Hungary — 3Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Hungary
We present ab-initio work concerning the anisotropy in the industrially significant antiferromagnet IrMn3, and results of an atomistic spin model parametrised using ab-initio data[1]. In particular, we obtain the surprising result that the cubic crystal symmetry is locally broken, leading to a strong second order anisotropy, K≈ 3× 108 erg/cc. The easy axis is oriented along the three different (100) axes for each of the three sublattices in the L12 structure. This anisotropy structure is confirmed by ab-initio calculations and reproduces the experimentally observed ground state spin structure[2].
Using the spin model, the response of individual antiferromagnetic grains to the exchange field of a reversing ferromagnet have been investigated. For the case of the fully compensated (111) interface, we discuss the distortion of the “T1” ground state and the possibility of exchange bias at such interfaces; the stability and reversal mechanisms of IrMn3 grains are also examined.
[1]L. Szunyogh, L. Udvardi et.al. Phys. Rev. B, submitted (2008)
[2]I. Tomeno, H.N. Fuke et.al. J. Appl. Phys 86 (1999) 3853