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Incommensurate modulated structure of the ferromagnetic shape-memory Ni2MnGa martensite |
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| Authors: | Lara Righi Franca Albertini Luigi Pareti Clemens Ritter Luis Morellon |
| Institution: | a Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università di Parma, Viale delle Scienze, I-43100 Parma, Italy b IMEM, Consiglio Nazionale delle Ricerche, Parco Area delle Scienze 37/A, I-43010 Fontanini, Parma, Italy c Intitut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France d Departamento de Fisica de la Materia Condensada-ICMA, Universidad de Zaragoza CSIC, 50009 Zaragoza, Spain |
| Abstract: | The ferromagnetic shape memory (MSM) alloy Ni2MnGa undergoes a martensitic transformation (MT) at T=220 K on cooling. The structure of this phase is studied by powder X-ray diffraction experiment. The analysis of the experimental data combined with the huge information reported in literature allowed to conclude that the Ni2MnGa martensite shows an incommensurate modulated structure closely related to a five-fold layered superstructure. The symmetry of the basic structure is found to be orthorhombic. The structure is refined by Rietveld method with superspace group Immm(00γ)s00 having a=4.2187(1) Å, b=5.5534(1) Å and c=4.1899(1) Å and modulation vector q=0.4248(3)c*. The results show that the modulation is mainly related to the periodic shuffling of the atomic layers perpendicular to the c-axis of the orthorhombic basic structure. |
| Keywords: | Ferromagnetic shape memory alloy Ni2MnGa Incommensurate modulation Rietveld refinement |
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