Reentrant spin glass transition and partial substitution induced superconductivity in magnetocaloric Mn₅Sn₃ alloys

Mn₅Sn_3−xIn_x (x = 0.1 and 0.25) alloys have been prepared and named as sample-1 and sample-2, respectively. Partial substitution of indium (In) and heat treatment conditions adopted have caused the alloys to crystallize with indium-containing-Mn_2−ySn phase and MnSn₂ phase. The magnetism in these alloys stem only from Mn_2−ySn. This phase has two Mn sites such that its magnetic structure and doping-induced disorderliness cause frustration and randomness resulting in reentrant spin glass transition in the alloys. Indium-doping has induced superconductivity in these samples, which is novel to occur in Mn₅Sn₃ systems. The upper critical fields of the two alloys are as low as 3.11 and 4.11 kOe and the superconducting transition temperatures are 5.6 and 5.9 K, respectively. Besides, long-range ordering of moments in two Mn sites of Mn_2−ySn phase has led to two separate transitions, and on the whole, the alloys are found to have complex magnetic ground state. The magnetocaloric properties are moderate, but indium-doping has increased the relative cooling power of these samples when compared to other Mn₅Sn₃ systems.