Neutron diffraction study on crystal structure and phase transformation in Ni-Mn-Ga ferromagnetic shape memory alloys
2007 (English)In: Powder Diffraction, ISSN 0885-7156, Vol. 22, no 4, 307-311 p.Article in journal (Refereed) Published
Crystal structure and phase transformation behaviors in two Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) with compositions of Ni48Mn30Ga22 and Ni53Mn25Ga22 (at. %) as a function of temperature were investigated by in situ neutron diffraction experiments. Neutron diffraction technique proves to be highly efficient in characterizing structural transformation in Ni-Mn-Ga FSMAs, which consist of nearby elements in the periodic table. Our neutron results show that Ni48Mn30Ga22 has a cubic, L-21 Heusler structure from 373 to 293 K. Its crystal structure changes into a seven-layered orthorhombic martensitic structure when cooled to 243 K, and no further transformation is observed upon cooling to 19 K. Neutron diffraction results also show that Ni53Mn25Ga22 has a tetragonal 14/mmm martensitic structure from 20 to 403 K. A pre-transformation around room temperature is observed from an abrupt jump in unit-cell volume of Ni53Mn25Ga22, which corresponds with an endothermic peak detected in a heated DSC curve.
Place, publisher, year, edition, pages
2007. Vol. 22, no 4, 307-311 p.
neutron powder diffraction, ferromagnetic shape memory alloy, crystal structure, martensitic transformation, Ni-Mn-Ga alloy
IdentifiersURN: urn:nbn:se:su:diva-55266DOI: 10.1154/1.2790932ISI: 000251571300007OAI: oai:DiVA.org:su-55266DiVA: diva2:406627
authorCount :62011-03-282011-03-072011-03-28Bibliographically approved