Ab Initio Predicted Impact of Pt on Phase Stabilities in Ni-Mn-Ga Heusler Alloys |
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Authors: | Biswanath Dutta Tilmann Hickel Peter Entel Jörg Neugebauer |
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Affiliation: | 1. Max-Planck-Institut für Eisenforschung GmbH, 40237, Düsseldorf, Germany 2. Faculty of Physics and CENIDE, University of Duisburg-Essen, 47048, Duisburg, Germany
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Abstract: | The paper discusses the stabilization of the martensite in Ni2MnGa at finite temperatures that is caused by the substitution of Ni by Pt. For this purpose a recently developed ab initio based formalism employing density functional theory is applied. The free energies of the relevant austenite and martensite phases of Ni1.75Pt0.25MnGa are determined incorporating quasiharmonic phonons and fixed-spin magnons. In addition the dependence of the transition temperatures on the Pt concentration is investigated. Though our results are in qualitative agreement with estimates based on ground-state energies, they clearly demonstrate that a proper treatment of finite temperature contributions is important to predict the martensitic transition quantitatively. |
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