Abstract:A series of polycrystalline sample SmCo1-xFexAsO (x=0, 0.05, 0.1, 0.2) was prepared by a solid-state reaction method. X-ray diffraction patterns indicate that all the samples have formed the ZrCuSiAs-type structure. The decrease of the lattice constant a and the increase of c are observed with the increased doping amount. Magnetic measurement results show that complicated magnetism consists of antiferromagnetic, ferromagnetic and paramagnetic between 5 and 300 K. Strong irreversibility in M-T curve is observed just below the Curie temperature. With Fe content increasing, antiferromagnetic order of SmCoAsO is suppressed, and its ferromagnetism is enhanced. M-H curves show that metamagnetic transition occurs below their antiferromagnetic transition temperature for samples with x<0.2, and the transition field decreases with increasing Fe content. When Fe content reaches to 0.2, no metamagnetic transition can be observed down to 5 K. All of the results are consistent with the existence of a metamagnetic critical end point at critical concentration which is close to 0.2.