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Phys. Rev. Lett. 102, 035702 (2009) [4 pages]

Understanding the Phase Transitions of the Ni2MnGa Magnetic Shape Memory System from First Principles

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M. A. Uijttewaal1,*, T. Hickel1, J. Neugebauer1, M. E. Gruner2, and P. Entel2
1Max-Planck-Institut für Eisenforschung GmbH, D-40237, Düsseldorf, Germany
2Physics Department and CENIDE, University of Duisburg-Essen, Campus 47048 Duisburg, Germany

Received 22 September 2008; revised 10 November 2008; published 22 January 2009

The free energies of the austenite, the (modulated) premartensite and the unmodulated martensite of Ni2MnGa are determined using density functional theory and including quasiharmonic phonons and fixed-spin-moment magnons. This approach very well reproduces the complete phase sequence (martensite↔premartensite↔austenite) of stoichiometric Ni2MnGa as a function of temperature. By analyzing the relevant free energy contributions, we also understand the delicate interplay of phonons and magnons driving both phase transitions.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.102.035702
DOI:
10.1103/PhysRevLett.102.035702
PACS:
64.60.Ej, 63.20.dk, 75.50.Cc, 81.30.Kf

*uijttewaal@mpie.de