Department of Physics, Loughborough University, UK.
J Phys Condens Matter. 2010 Dec 22;22(50):506001. doi: 10.1088/0953-8984/22/50/506001. Epub 2010 Nov 26.
Magnetization and high resolution neutron powder diffraction measurements on the magnetic shape memory alloy Mn(2)NiGa have confirmed that it is ferromagnetic with a Curie temperature above 500 K. The compound undergoes a broad structural phase transformation ΔT ∼ 90 K with a mean transition temperature T(M) ∼ 270 K. The high temperature parent phase is cubic (a = 5.937 Å) and has a modified L 2(1) structure. At 500 K the ordered magnetic moment essentially all on the 4a site is 1.35 μ(B)/Mn. The low temperature martensite has space group I4/mmm and is related to the cubic phase through a Bain transformation a(tet) = (a(cub) + b(cub))/2, b(tet) = (a(cub) - b(cub)) and c(tet) = c(cub) in which the change in cell volume is < 2.6%. In this structure at 5 K the ordered moment of ≈2.3 μ(B) is again found to be confined to the sites with full Mn occupation and is aligned parallel to c. Neutron diffraction patterns obtained at 5 K suggested the presence of a weak incommensurate antiferromagnetic phase characterized by either a ((1/3)0(1/3)) or (00(1/3)) propagation vector.
对 Mn(2)NiGa 磁形状记忆合金的磁化和高分辨率中子粉末衍射测量证实，它是铁磁性的，居里温度高于 500 K。该化合物经历了一个宽的结构相变 ΔT ∼ 90 K，平均转变温度 T(M) ∼ 270 K。高温母相为立方（a = 5.937 Å），具有改良的 L 2(1)结构。在 500 K 时，有序磁矩几乎全部位于 4a 位，为 1.35 μ(B)/Mn。低温马氏体具有空间群 I4/mmm，通过 Bain 转变与立方相相关，a(tet) = (a(cub) + b(cub))/2，b(tet) = (a(cub) - b(cub)) 和 c(tet) = c(cub)，其中细胞体积的变化<2.6%。在这个结构中，在 5 K 时，有序矩约为 2.3 μ(B)，再次被发现局限于完全 Mn 占据的位置，并与 c 平行排列。在 5 K 获得的中子衍射图谱表明存在一个弱的非共格反铁磁相，其特征在于 ((1/3)0(1/3)) 或 (00(1/3)) 传播矢量。
