Magnetic, electronic transport and magneto-transport behaviors of Co_xFe_1-xMnP compounds

Magnetic, electronic transport and magneto-transport behaviors of Co_xFe_1-xMnP (0.40 ≤ x ≤ 0.75) compounds have been investigated systematically. Co_0.4Fe_0.6MnP is antiferromagnetic below its Néel temperature of 310 K, while an anomalous increase of resistivity occurs with decreasing the temperature from 350 to 190 K, which is attributed to the effect of critical spin fluctuation on resistivity. Increasing Co concentration gives rise to dramatic changes of magnetic, electronic transport and magneto-transport behaviors. With increasing temperature, a magnetic phase transition from an antiferromagnetic state to a ferromagnetic one takes place at about 280, 218 and 180 K for Co_0.55Fe_0.45MnP, Co_0.65Fe_0.35MnP and Co_0.75Fe_0.25MnP, respectively. Moreover, the compounds experience a metal-insulator transition at 26, 29, 35 and 45 K, respectively, for x = 0.40, 0.55, 0.65 and 0.75. Maximum magnetoresistance ratios of -8.1%, -4.7% and -2.9% are observed in the Co_0.75Fe_0.25MnP, Co_0.65Fe_0.35MnP and Co_0.55Fe_0.45MnP compounds at an external magnetic field of 5 T. The mechanisms of magnetoresistance behaviors are interpreted in terms of the suppression of spin fluctuations in the antiferromagnets by the applied fields.