TY - JOUR
T1 - Structural modulations and magnetic properties of off-stoichiometric Ni-Mn-Ga magnetic shape memory alloys
AU - Pramanick, A.
AU - Wang, X. P.
AU - An, K.
AU - Stoica, A. D.
AU - Yi, J.
AU - Gai, Z.
AU - Hoffmann, C.
AU - Wang, X. L.
PY - 2012/4/16
Y1 - 2012/4/16
N2 - A comparative description of the crystallographic structural details and the magnetic properties of Ni-Mn-Ga magnetic shape memory alloys are necessary to understand the physical origins of their magnetoelastic properties. The crystallographic structural details of an off-stoichiometric Ni 2Mn 1.14Ga 0.86 alloy have been obtained from the refinement of high-resolution single-crystal neutron diffraction data, following a (3+1)-dimensional [(3+1)-D] superspace formalism. In particular, the structure adopts a P2/m(α0γ)00 superspace group symmetry with the following fundamental lattice parameters: a = 4.255(4) b = 5.613(4) c = 4.216(3) a commensurate periodicity of 5M, and a modulation wave vector of q - =2/5c - . The magnetic properties of the crystal are characterized from magnetic susceptibility measurements, as well as from neutron diffraction intensities. The overall magnetic moment per unit cell is 2.7 μ B per Ni 2Mn 1.14Ga 0.86 formula unit and the magnetic moments are aligned along the b axis. The modulations of the atomic site displacements, site occupancies, and magnetic moments are elucidated from a (3+1)-D refinement of the neutron diffraction intensities. In addition to atomic displacements corresponding to shear waves along 110 distortions of the Ni-centric tetrahedra are also evident. Physical interpretations for the different structural distortions and their relationship to magnetic properties are discussed.
AB - A comparative description of the crystallographic structural details and the magnetic properties of Ni-Mn-Ga magnetic shape memory alloys are necessary to understand the physical origins of their magnetoelastic properties. The crystallographic structural details of an off-stoichiometric Ni 2Mn 1.14Ga 0.86 alloy have been obtained from the refinement of high-resolution single-crystal neutron diffraction data, following a (3+1)-dimensional [(3+1)-D] superspace formalism. In particular, the structure adopts a P2/m(α0γ)00 superspace group symmetry with the following fundamental lattice parameters: a = 4.255(4) b = 5.613(4) c = 4.216(3) a commensurate periodicity of 5M, and a modulation wave vector of q - =2/5c - . The magnetic properties of the crystal are characterized from magnetic susceptibility measurements, as well as from neutron diffraction intensities. The overall magnetic moment per unit cell is 2.7 μ B per Ni 2Mn 1.14Ga 0.86 formula unit and the magnetic moments are aligned along the b axis. The modulations of the atomic site displacements, site occupancies, and magnetic moments are elucidated from a (3+1)-D refinement of the neutron diffraction intensities. In addition to atomic displacements corresponding to shear waves along 110 distortions of the Ni-centric tetrahedra are also evident. Physical interpretations for the different structural distortions and their relationship to magnetic properties are discussed.
UR - http://www.scopus.com/inward/record.url?scp=84860290540&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.85.144412
DO - 10.1103/PhysRevB.85.144412
M3 - Article
AN - SCOPUS:84860290540
SN - 1098-0121
VL - 85
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 14
M1 - 144412
ER -