Neutron diffraction study of a non-stoichiometric Ni-Mn-Ga MSM ALLOY

Pnina Ari-Gur, V. Ovidiu Garlea, Ashley Coke, Yanling Ge, Ilkka Aaltio, Simo Pekka Hannul, Huibo Cao, Amila Sb Madiligama, Victor Koledov

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations

Abstract

The structure and chemical order of a Heusler alloy of non-stoichiometric composition Ni-Mn-Ga were studied using constant-wavelength (1.538 Å) neutron diffraction at 363K and the diffraction pattern was refined using the FullProf software. At this temperature the structure is austenite (cubic) with Fm-3m space group and lattice constant of a = 5.83913(4) [Å]. The chemical order is of critical importance in these alloys, as Mn becomes antiferromagnetic when the atoms are closer than the radius of the 3d shell. In the studied alloy the refinement of the site occupancy showed that the 4b (Ga site) contained as much as 22% Mn; that significantly alters the distances between the Mn atoms in the crystal and, as a result, also the exchange energy between some of the Mn atoms. Based on the refinement, the composition was determined to be Ni1.91Mn1.29Ga0.8.

Original languageEnglish
Title of host publicationEuropean Symposium on Martensitic Transformations, ESOMAT 2012
EditorsSergey Prokoshkin, Natalia Resnina
PublisherTrans Tech Publications Ltd
Pages103-107
Number of pages5
ISBN (Print)9783037856109
DOIs
StatePublished - 2013
Event9th European Symposium on Martensitic Transformations, ESOMAT 2012 - Saint-Petersburg, Russian Federation
Duration: Sep 9 2012Sep 16 2012

Publication series

NameMaterials Science Forum
Volume738-739
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Conference

Conference9th European Symposium on Martensitic Transformations, ESOMAT 2012
Country/TerritoryRussian Federation
CitySaint-Petersburg
Period09/9/1209/16/12

Keywords

  • Chemical order
  • Magnetic shape memory
  • Neutron diffraction
  • Ni-Mn-Ga alloy
  • Rietveld method
  • Structure refinement

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