Electrical Transport and Magnetic Properties of La_0.67Ca_0.33Mn_1-xCr_xO₃ and La_0.67+xCa_0.33-xMn_1-xCr_xO₃（0.04≤x≤0.08）

XIAO Xun1,YUAN Songliu2,YIN Shiyan2,CHEN Ling2,REN Guangming2, MIAO Juhong2,YU Gongqi2 (1.School of Physics Science and Technology,Yangtze University,Jingzhou 434023,China; 2.Department of Physics,Huazhong University of Science and Technology,Wuhan 430074,China)

摘 要：A comparative study for two different series,La 0.67 Ca 0.33 Mn 1-x Cr x O3 and La 0.67+x Ca 0.33-x Mn 1- x Cr x O 3 ,is performed with x changing from 0.04 to 0.08 through measurements of zero-field resistivity（ρ）, magnetoresistance（MR）and ac susceptibility（χ）as functions of temperature（T）.For the second group,a single insulator-metal transition was characterized by the resistivity maximum appears inρvs.T curve.For the first group,besides the resistivity peak appearing at higher temperatures,the sample shows evidence for the existence of another peak appearing at lower temperatures.Compared to the first group,the second group shows a significant enhancement in MR effect,while the measurement ofχ-T dependence does not display obvious differences for the two series.Different behaviors observed in the two series are discussed by considering possible exchange interaction between Mn3+ion and Cr3+ion.

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