Structural,magnetic,and transport properties of perovskite La_(2/3)Ca_(1/_3)Mn_(1-x)Si_(x)O_(3)(x=0,0.025,0.05)have been studied.The incorporation of Si decreases the overall resistivity,but obviously increases the Cu...Structural,magnetic,and transport properties of perovskite La_(2/3)Ca_(1/_3)Mn_(1-x)Si_(x)O_(3)(x=0,0.025,0.05)have been studied.The incorporation of Si decreases the overall resistivity,but obviously increases the Curie temperature(TC),metal-insulator transition temperature(TP),and the magnetoresistance ratio MR(defined as[R(0)-R(H)]/R(0))near room temperature.Comparing with La_(2/3)Ca_(1/_3)MnO_(3)the TC,TP,and MR of the sample with x=0.05 increase by 30,45K,and 20%,respectively.Lattice effects may play a more important role than the magnetic dilution in the case of low Si substitution.展开更多
The magnetoresistance(MR)behavior of La_((2-x)/3)Bi_(x/3)Ca_(l/3)MnO_(3)(x=0.4)compound was investigated.The compound exhibits complex magnetic transitions,i.e.,paramagnetic-canted ferromagnetic-ferromagnetic-spin gla...The magnetoresistance(MR)behavior of La_((2-x)/3)Bi_(x/3)Ca_(l/3)MnO_(3)(x=0.4)compound was investigated.The compound exhibits complex magnetic transitions,i.e.,paramagnetic-canted ferromagnetic-ferromagnetic-spin glass transitions.The temperature dependence of resistivity of the compound indicates a semiconducting behavior,and no semiconductor-metal transition was associated with these magnetic transitions.The magnetoresistance ratio exhibits a critical maximum corresponding to the canted ferromagnetic transition.A MR ratio as large as 86%was observed at 85 K.The temperature dependence of MR ratio is well described by the relation of(ρo-ρH)/ρo=A(M/M_(s))^(2).展开更多
基金Supported by National Natural Science Foundation of China under Grant Nos.59702011 and 59525101the 973 State Key Program of Basic Research of China(G1998061314).
文摘Structural,magnetic,and transport properties of perovskite La_(2/3)Ca_(1/_3)Mn_(1-x)Si_(x)O_(3)(x=0,0.025,0.05)have been studied.The incorporation of Si decreases the overall resistivity,but obviously increases the Curie temperature(TC),metal-insulator transition temperature(TP),and the magnetoresistance ratio MR(defined as[R(0)-R(H)]/R(0))near room temperature.Comparing with La_(2/3)Ca_(1/_3)MnO_(3)the TC,TP,and MR of the sample with x=0.05 increase by 30,45K,and 20%,respectively.Lattice effects may play a more important role than the magnetic dilution in the case of low Si substitution.
基金Supported by the National Natural Science Foundation of China under Grant No.29401006.
文摘The magnetoresistance(MR)behavior of La_((2-x)/3)Bi_(x/3)Ca_(l/3)MnO_(3)(x=0.4)compound was investigated.The compound exhibits complex magnetic transitions,i.e.,paramagnetic-canted ferromagnetic-ferromagnetic-spin glass transitions.The temperature dependence of resistivity of the compound indicates a semiconducting behavior,and no semiconductor-metal transition was associated with these magnetic transitions.The magnetoresistance ratio exhibits a critical maximum corresponding to the canted ferromagnetic transition.A MR ratio as large as 86%was observed at 85 K.The temperature dependence of MR ratio is well described by the relation of(ρo-ρH)/ρo=A(M/M_(s))^(2).
