The Effect of Partial Substitution of Ni by Co on the Magnetic and Electrical Properties of ${\rm Ni}_{50}{\rm Mn}_{35}{\rm In}_{15}$ 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.