Dresden 2009 – scientific programme

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MA: Fachverband Magnetismus

MA 26: Magnetic Shape Memory Alloys II

MA 26.4: Talk

Wednesday, March 25, 2009, 15:30–15:45, HSZ 103

Modelling the phase diagram of Ni-Mn-X (X = In, Sn, Sb) alloys:*A q-state Potts model monte Carlo study — •P. Entel¹, V. D. Buchelnikov², S. V. Taakaev², V. V. Sokolovskiy², A. Hucht¹, M. Ogura³, H. Akai³, M. E. Gruner¹, and S. K. Nayak¹ — ¹Physics Department, University of Duisburg-Essen, 47048 Duisburg, Germany — ²Department of Condensed Matter Physics, Chelyabinsk State University, 454021 Chelyabinsk, Russia — ³Department of Physics, Osaka University, Osaka 560-0043, Japan

On the basis of Monte Carlo simulations using Heisenberg and Potts model Hamiltonians, we investigate the complex temperature dependence of the phase diagram of Ni-Mn-X (X = In, Sn, Sb) Heusler alloys. For Mn excess concentration, we find Mn atoms on the X sites, whose magnetic moments interact antiferromagnetically with the Mn spin moments on the Mn sublattice. Using ab initio data for the magnetic exchange interactions, it is shown that this antiferromagnetic exchange is responsible for metamagnetic behavior and a series of magnetic phase transitions, which compete or act in favor of the martensitic transformation being present in the Heusler alloys. This scenario is finally responsible for the occurrence of magneto-structural phase transitions in this class of ferromagnetic Heusler alloys.