Journal of Physics Condensed Matter · 2006 · 231 citations · 11 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsMagnetic MaterialsSolid State PhysicsFerromagnetic MaterialsFerromagnetismMagnetic Properties Of SolidsMagnetism In SolidsMagnetism Of Inorganic CompoundsPhase TransitionsFerromagnetic Phase TransitionsMagnetic Shape Memory AlloysMagnetic Shape Memory TransformationMagnetostructural TransitionsOrthorhombic LatticesOrthorhombic SystemPhase Transition TemperatureTransition Metal Magnetism
Ni₂Mn₁.₄₄Sn₀.₅₆ adopts a high‑temperature cubic L2₁ structure with excess Mn on Sn sites and transforms to an orthorhombic Pmma phase via a Bain‑type distortion at low temperatures. Magnetization and neutron diffraction show the compound is ferromagnetic below 319 K, undergoes a structural transition at 221 K on cooling (239 K on warming), with Mn moments of 1.88 μB at 4(a) sites and 0.53 μB at 4(b) sites, and a ~0.5 % volume change that reduces spontaneous magnetization.
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 Å, 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) μB but it was only 0.53(18) μB/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.
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Magnetic order and phase transformation in Ni<sub>2</sub>MnGa
P. J. Webster, K.R.A. Ziebeck, S.L. Town et al. · Philosophical Magazine B · 1984 · 1.2K citations