Magnetic and structural phase diagram of antiperovskites ZnCFe3−xCox (0 ≤ x ≤ 3): The combined negative magnetoresistance and large room-temperature magnetocaloric effect in x = 0.5

Abstract Effects of Co doping on the crystal structure, magnetic, electrical transport properties, and magnetocaloric effect (MCE) of antiperovskite ZnCFe 3− x Co x (0 ≤  x  ≤ 3) were investigated. The value of lattice constant decreases with increasing x . The Curie temperature ( T C ) decreases from 358 K in ZnCFe 3 to 5 K in ZnCCo 3 and the saturated magnetization declines monotonously. The reduced ferromagnetic state is explained by the band filling effect resulted from the Co substitution. For x  ≥ 2.3, the negative magnetoresistance (MR) below T C starts to increase as x or magnetic field increases, reaching −16% for x  = 2.9 under H  = 45 kOe, which is three times larger than that of GaCMn 3 at 250 K. MCE was investigated for selected compositions. The temperature range of MCE is tuned covering 5–350 K as a function of Co-level. Although the maximal entropy change decreases a little with increasing x , the refrigeration ranges across room temperature. At the optimal composition x  = 0.5, T C is 312 K with a magnetic entropy change of 2.09 J/kg K and relative cooling power (RCP) of 283 J/kg (Δ H  = 45 kOe), make it a room-temperature MCE candidate.