Composition dependence of transition temperatures on quaternary Co-Fe-Ni-Ga melt-spun alloys

Abstract

The composition dependence of transition temperatures on quaternary Co-Fe-Ni-Ga melt-spun alloys with constant Ga content are examined. A few at.% of Fe replacement for Co in Co50Ni22Ga28 drastically reduce martensitic transformation temperature (TM) whereas ferromagnetic transition temperature (Tc) remains above 400 K. Increasing Ni instead of Co in Fe doped specimen can raise TM around room temperature again. Further increase of Fe content with this manner, the alloys finally connected to ternary Ni-Fe-Ga of ferromagnetic shape memory region. The martensitic transition start temperature (MS) of Co-Fe-Ni-Ga28 alloys show good correlation with the valence electron ratio (e/a). The MS vs e/a plot clearly shows that trend lines are separated for each Fe content, and intervals of trend lines seem to be proportional to Fe content at lower Fe region. The Tc and saturation magnetization of Co-Fe-Ni-Ga28 alloys show almost linear relation with magnetic valence Zm.