Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 8: Magnetic Coupling Phenomena / Exchange Bias
MA 8.9: Vortrag
Montag, 23. März 2009, 17:15–17:30, HSZ 401
Successive antiferromagnetic phase transitions in α-MnS probed by the exchange bias effect — •Pavel Borisov1, Xi Chen2, Andreas Hochstrat1, and Wolfgang Kleemann1 — 1Angewandte Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany — 2Department of Physics, South China University of Technology, Guangzhou, P.R. China
The exchange bias (EB) probe is applied to test the magnetic properties of a material with two successive antiferromagnetic (AF) phase transitions [1]. α-MnS has been claimed to reveal a second-order one at TC1 = 152 K and a discontinuous one at TC2 = 129 K. A cubic paramagnetic state (phase I) and a slightly rhombohedrally distorted fcc AF spin order (phase II) similar to that in NiO are observed at T > TC1 and TC2 < T < TC1, respectively. However, there was a debate about the spin structure below TC2 (phase III).
The EB effect of the heterolayer structure α-MnS(111)/Fe(1.5 nm)/Pt(3 nm) arises below TC1 and maximizes at TC2, below which it vanishes steplike in parallel with a sudden increase of the coercive field of the Fe layer, HC. EB recovers again below the second blocking temperature, TB2 ≈ 25 K. The abrupt vanishing of HEB and the step-like increase of HC below TC2 comply with a first-order AF spin reorientation transition of α-MnS to phase III. The strong enhancement of HC observed in the phase III corroborates the conjectured multi-k spin structure.
[1] X. Chen, A. Hochstrat, P. Borisov, W. Kleemann, submitted to Appl. Phys. Lett. (2008).