The doping effects of Sm in La 0.67 Ca 0.33 MnO 3 oxide were studied. The results show that with increasing the doping amount of Sm the phase transition temperature of metal insulator for the materials decre...The doping effects of Sm in La 0.67 Ca 0.33 MnO 3 oxide were studied. The results show that with increasing the doping amount of Sm the phase transition temperature of metal insulator for the materials decreases monotonically, the corresponding peak resistance increases rapidly, the Curie temperature decreases monotonically, and the magneto resistance ratio increases quickly. The effects of Sm doping can be explained in terms of lattice effects.展开更多
La 0.5- x Y x Ba 0.5 CoO 3 polycrystals were prepared by solid state reaction. The substituting effects of Y for La on the magnetic and transport properties of the materials were studied systematically...La 0.5- x Y x Ba 0.5 CoO 3 polycrystals were prepared by solid state reaction. The substituting effects of Y for La on the magnetic and transport properties of the materials were studied systematically. The results indicate that substitution of Y induces two effects. Firstly, the charge transfer from Y to 3d orbital of Co happens. This causes the molecular magnetic moment to decrease. Secondly, the antiferromagnetic exchange interaction of Co ions appears. When the content of Y is less than or equal to 30%, the non colinear structure of spins in materials is observed. When the content of Y is greater than 30%, the materials transit from predominant ferromagnetic state to predominant antiferromagnetic one. The conductive mechanism for the materials with different content of Y belongs to the variable range hopping conduction of polarons. The resistivity of materials increases sharply with increasing Y content.展开更多
文摘The doping effects of Sm in La 0.67 Ca 0.33 MnO 3 oxide were studied. The results show that with increasing the doping amount of Sm the phase transition temperature of metal insulator for the materials decreases monotonically, the corresponding peak resistance increases rapidly, the Curie temperature decreases monotonically, and the magneto resistance ratio increases quickly. The effects of Sm doping can be explained in terms of lattice effects.
文摘La 0.5- x Y x Ba 0.5 CoO 3 polycrystals were prepared by solid state reaction. The substituting effects of Y for La on the magnetic and transport properties of the materials were studied systematically. The results indicate that substitution of Y induces two effects. Firstly, the charge transfer from Y to 3d orbital of Co happens. This causes the molecular magnetic moment to decrease. Secondly, the antiferromagnetic exchange interaction of Co ions appears. When the content of Y is less than or equal to 30%, the non colinear structure of spins in materials is observed. When the content of Y is greater than 30%, the materials transit from predominant ferromagnetic state to predominant antiferromagnetic one. The conductive mechanism for the materials with different content of Y belongs to the variable range hopping conduction of polarons. The resistivity of materials increases sharply with increasing Y content.
