Effect of partial substitution of silicon by other sp-valent elements on structure, magnetic properties and electrical resistivity of Co2FeSi Heusler alloys

The effect of partial substitution (50%) of Si by other sp-valent elements such as Al, Ga, Ge, In and Sn on structure, magnetic properties and electrical resistivity of full Heusler type Co2FeSi alloys was investigated. The results revealed that these alloys (except Sn substituted alloy) consist of mostly L21 ordered phase along with some B2 type disordered phase. The highest L21 ordering was seen in Co2FeSi0.5Ge0.5 alloy. The magnetization studies showed all alloys obey the Slater-Pauling rule at 4 K except for Sn substituted alloy. However, at room temperature, only Ga, Ge and Al substituted alloys followed the Slater-Pauling rule. Electrical transport studies revealed the presence of half-metallic behavior at low temperatures in all alloys. However, half-metallicity was preserved to some extent at room temperature only in Ga and Ge substituted Co2FeSi alloys.