The Effect of Partial Substitution of Ni by Co on the Magnetic and Electrical Properties of Heusler Alloy

In this paper, we have explored the effects of the partial substitution of Ni for a small amount of Co in Ni₅₀Mn₃₅In₁₅ on its structural, magnetic, and electrical properties by using room temperature X-ray diffraction, temperature- and field-dependent magnetization, M(T,H), and resistivity ¿(T,H) measurements in magnetic fields up to 5 T, and in the temperature interval 5-400 K. A small amount of Co (~4%) doping in the Ni site decreases T_M and increases T_C. For Ni₄₈Co₂Mn₃₅In₁₅, a large MR was found to be about -53% at ¿H = 1 T (at T = 275 K) and more than -70% at the same temperature for ¿H = 5 T. The substitution of Co in the Ni position enhances the magnetization jump up to 77 emu/g across the martensitic transformation. Magnetization measurements revealed that the large magnetoresistance value could be due to a metamagnetic-like transition, where the system transforms from a state that contains antiferromagnetically coupled regions to a purely ferromagnetic state. The change in magnetic and electrical properties due to the doping of the Co atom in Ni-Mn-In-based Heusler alloys is discussed in this paper.