Atomic ordering and magnetic properties of quaternary Heusler alloys NiCuMnZ (Z=In, Sn, Sb)

• Yuexing Ma^a, 
• Hongyue Hao^a, 
• Yuepeng Xin^a, 
• Hongzhi Luo^a, b, , , 
• Heyan Liu^a, 
• Fanbin Meng^a, 
• Enke Liu^b

• ^a School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, PR China
• ^b Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, PR China

Received 20 January 2017, Revised 22 March 2017, Accepted 25 March 2017, Available online 30 March 2017

Abstract

A series of quaternary Heusler alloys NiCuMnZ (Z = In, Sn, Sb) have been prepared experimentally. Their structural and magnetic properties have been investigated by XRD, magnetic measurements and first-principles calculations. NiCuMnZ all crystallize in a cubic Heusler structure. But the atomic ordering in them is different and related to the main group element Z. NiCuMnSb is highly ordered while NiCuMnIn and NiCuMnSn have a degree of Cu-Mn disorder in the lattice. In these alloys, Cu atom has strong preference for the B (0.25, 0.25, 0.25) site, though Cu has more valence electrons than Mn and Ni. The saturation magnetization M_s at 5 K is 3.99μ_B/f.u., 4.20μ_B/f.u. and 4.02μ_B/f.u. for NiCuMnSb, NiCuMnSn and NiCuMnIn, respectively. First-principles calculations suggest that the large total moments mainly come from the contribution of Mn. The T_C decreases rapidly from 716 K in NiCuMnSb to 340 K in NiCuMnIn, relating to the increasing degree of atomic disorder in their lattice. But the partial moments of Mn are always in ferromagnetic coupling though they are nearest neighbors in partly disordered NiCuMnSn and NiCuMnIn.

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