Effect of Pt doping Ni on the structural and magnetic properties of hexagonal MnNiGa alloy

• Main Authors: Z.H. Liu, Q. Liu, Q.Q. Zhang, J.G. Tan, L.H. Liu
• Format: Article
• Language: English
• Published: Elsevier 2019-03-01
• Series: Results in Physics
• Online Access: http://www.sciencedirect.com/science/article/pii/S2211379718332765

The structure and magnetic properties Mn1.2PtxNi1-xGa (x = 0, 0.2, 0.5, 1) alloys prepared by melting-spinning method were systematically studied. X-ray diffraction experiments confirmed that all the alloys exhibited hexagonal structure. Both a and c axes expanded with the increase of Pt content, which resulted in the increase of distance between Mn-Mn atoms in neighboring layers, thus a decrease of Curie temperature due to the weakening of ferromagnetic exchange interaction between Mn-Mn was observed. The coercivity of Mn1.2NiGa is about 300 Oe at 5 K, and it is enhanced to 8000 Oe in Mn1.2PtGa alloy. Simultaneously, the saturation magnetic field was increased by Pt doping, suggesting the enhancement of magnetocrystalline anisotropy. It is suggested that the large coercivity is attributed to the pinning of glass phase on the ferromagnetic phase and the increase of spin-orbit coupling. The glass phase transition temperature decreases with increasing Pt content, which makes the temperature stability of coercivity in Mn1.2PtGa is not so good as in Mn1.2Pt0.5Ni0.5Ga alloy. Keywords: Mn-Pt-Ga alloy, Stability of coercivity, Glassy ferromagnetism