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

Effects of Co doping on the crystal structure, magnetic, electrical transport properties, and magnetocaloric effect (MCE) of antiperovskite ZnCFe3-xCox (0 <= x <= 3) were investigated. The value of lattice constant decreases with increasing x. The Curie temperature (T-C) decreases from 358 K in ZnCFe3 to 5 K in ZnCCo3 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 GaCMn3 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 (Delta H = 45 kOe), make it a room-temperature MCE candidate. (C) 2016 Elsevier B.V. All rights reserved.