The magnetic and structural properties of the magnetic shape memory compound Ni2Mn1.44Sn0.56

• Published in: Journal of physics. Condensed matter 2006-02, Vol.18 (7), p.2249-2259
• Main Authors: Brown, P J, Gandy, A P, Ishida, K, Kainuma, R, Kanomata, T, Neumann, K-U, Oikawa, K, Ouladdiaf, B, Ziebeck, K R A
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Magnetic properties and materials; Martensitic transformations; Materials science; Other ferromagnetic metals and alloys; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Studies of specific magnetic materials
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/18/7/012

Magnetization and high resolution neutron powder diffraction measurements on the magnetic shape memory compound Ni2Mn1.44Sn0.56 have confirmed that it is ferromagnetic below 319 K and undergoes a structural phase transition which takes place at TM = 221 K on cooling and 239 K on warming. The high temperature phase has the cubic L 21 structure, a = 5.973 A, with the excess manganese atoms occupying the 4(b) tin sites. In the cubic phase at 245 K the manganese moments at both sites were found to be ferromagnetically aligned. The magnetic moment at the 4(a) sites was 1.88(10) muB but it was only 0.53(18) muB/Mn at the 4(b) sites. The low temperature phase stable below TM has an orthorhombic structure with space group Pmma related to the cubic phase through a Bain transformation aortho = (acub+bcub)/2; bortho = ccub; cortho = (acub- bcub). The change in cell volume in the transition is only 0.5%, suggesting that the atomic moments are unchanged although the spontaneous magnetization drops significantly.