Neutron Diffraction Study of a Non-Stoichiometric Ni-Mn-Ga MSM Alloy

Pnina Ari-Gur; V. Ovidiu Garlea; Ashley Coke; Yan Ling Ge; Ilkka Aaltio; Simo Pekka Hannula; Hui Bo Cao; Amila S.B. Madiligama; Victor Koledov

doi:10.4028/www.scientific.net/MSF.738-739.103

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HomeMaterials Science ForumMaterials Science Forum Vols. 738-739Neutron Diffraction Study of a Non-Stoichiometric...

Neutron Diffraction Study of a Non-Stoichiometric Ni-Mn-Ga MSM Alloy

Abstract:

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 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

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Periodical:

Materials Science Forum (Volumes 738-739)

Pages:

103-107

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.738-739.103

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Online since:

January 2013

Authors:

Pnina Ari-Gur, V. Ovidiu Garlea, Ashley Coke, Yan Ling Ge, Ilkka Aaltio, Simo Pekka Hannula, Hui Bo Cao, Amila S.B. Madiligama, Victor Koledov

Keywords:

Chemical Order, Magnetic Shape Memory, Neutron Diffraction, Ni-Mn-Ga Alloy, Rietveld Method, Structure Refinement

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