Influences of Cu doping on structure and phase transition of Ni-Fe-Ga alloy

Abstract

The structure and phase transition of Ni55-xCuxFe18Ga27 alloys prepared by arc-melting and melt-spinning techniques were systematically investigated in this paper. For arc-melting Ni55-xCuxFe18Ga27 (x=0,2.5,3.2,3.5,4,7,10,11,14,16) alloys, the martensitic transformation temperature reduced gradually from 292 K to 125 K with increasing Cu content. Substitution of Ni by Cu enhanced the exchange interaction among neighboring atoms in the transition metals, leading to increasing Curie temperature, except for some individual cases. This characteristic demonstrates that Ni55-xCuxFe18Ga27 alloys retain their ferromagnetism at even high temperature. The structure of melt-spinning Ni55-xCuxFe18Ga27 (x=1,2,3,4) alloys maintains pure L21-type with increasing lattice constant, which overcomes the γ phase in arc-melting samples. The increase of lattice constant in ribbon reduces exchange interaction between 3d electrons in the transition metals, thus decreases the martensitic transformation temperature.