Effects of Co doping on the magnetic properties, entropy change, and magnetocaloric effect in Mn₃Sn_1-xCo_xC_1.1 compounds

The Mn₃Sn_1-xCo_xC_1.1 compounds are synthesized by a solid-state reaction method. The effects of Co doping on the magnetic properties, phase transition and entropy change are investigated in Mn₃Sn_1-xCo_xC_1.1 compounds. The Curie temperature first decreases from 283 K to 212 K (Mn₃Sn_0.9Co_0.1C_1.1) with increasing the Co concentration, and then increases to 332 K (Mn₃Sn_0.2Co_0.8C_1.1) with further increasing the Co concentration in Mn₃Sn_1-xCo_xC_1.1. The first-order transition of Mn₃Sn_1-xCo_xC_1.1 gradually changes into the second-order transition, in the mean time, the entropy change decreases and the phase transition region broadens from 9 K to 300 K with increasing the Co content. Both the magnetic entropy change and broadening the transition temperature span can influence the relative cooling power R. Finally we obtain the large R = 103 J/kg (H = 1.6 MA/m) in Mn₃Sn_0.8Co_0.2C_1.1, which could be used as the room-temperature magnetic refrigerant materials.