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

Highlights: • Compositions of Co-Fe-Ni-Ga alloys which connect between ferromagnetic shape memory region of Co-Ni-Ga and Ni-Fe-Ga. • Martensite transformation temperatures are almost proportional to electron to atom ratio. • The trend lines are separated for each Fe contents. 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 (T_M) whereas ferromagnetic transition temperature (Tc) remains above 400 K. Increasing Ni instead of Co in Fe doped specimen can raise T_M 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 (M_S) of Co-Fe-Ni-Ga₂₈ alloys show good correlation with the valence electron ratio (e/a). The M_S 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 Z_m.