Magnetic, Electrical and Structural study of Mn-Co-Sn Heusler Nanomaterials

The nano-structured Mn$_{3-x}$Co$_{x}$Sn (x = 0, 0.3, 0.5, 0.7, 1.0) alloys were prepared using arc-melting, melt-spinning and thermal annealing. Mn$_{3}$Sn is stable in the hexagonal structure and it shows an antiferromagnetic spin order at room temperature. Mn$_{3-x}$Co$_{x}$Sn alloys maintained a hexagonal structure upon substituting Mn with Co up to x = 0.7, and then it transformed to cubic phases at x = 1.0. At room temperature Mn$_{3-x}$Co$_{x}$Sn (x = 0.5, 0.7, 1.0) exhibited ferromagnetic spin order. Mn$_{2.3}$Co$_{0.7}$Sn sample showed Curie temperature of 640 K. However, the transition temperatures are suppressed to 600 K for Mn$_{2.5}$Co$_{0.5}$Sn and Mn$_{2.0}$Co$_{1.0}$Sn. The room temperature saturation magnetization measured at 7.0 T increases with increasing amount of Co substitution, varying from 13 emu/g (x = 0.5), 25 emu/g (x = 0.7), and 50 emu/g (x = 1.0), respectively. The electrical resistivity of all the Co-substituted samples depends on temperature and decreases with increasing temperature from 5 K to room temperature. Interestingly, there observed a rapid upturn in the resistivity at 250 K for Mn$_{2.5}$Co$_{0.5}$Sn.