Magnetic properties and magnetoresistance effect of La₂Co_{1− x} Mg _x MnO₆ (0.1  ⩽   x   ⩽  1.0)

Double perovskite La₂Co_1−x Mg_x MnO₆ samples with different compositions ( x   =  0.1, 0.2, 0.3, 0.5, 0.7, 1.0) were synthesized by the standard solid-state reaction method. The samples ( x   =  0.1, 0.2, 0.3, 0.5, 0.7) exhibit obvious ferromagnetic behavior. The remanent magnetization, coercive field and Curie temperature gradually decrease with increasing the Mg-substitution. The appropriate amount of Mg-substitution can increase the saturation magnetization. The types of interactions changed with Mg-substitution, which makes the La₂MgMnO₆ sample exhibit clear antiferromagnetism. A slightly enhanced negative magnetoresistance effect (approximately 17%) of the La₂Co_0.9Mg_0.1MnO₆ sample was observed at 200 K and 7 T. The pronounced linear magnetoresistance effect is attributed to the suppression of spin-fluctuations by the magnetic field. (paper)