稀土学报(英文版)
稀土學報(英文版)
희토학보(영문판)
JOURNAL OF RARE EARTHS
2004年
6期
803-807
,共5页
黄宝歆%刘宜华%张汝贞%原晓波%王成建%梅良模
黃寶歆%劉宜華%張汝貞%原曉波%王成建%梅良模
황보흠%류의화%장여정%원효파%왕성건%매량모
ceramic materials%colossal magnetoresistance%spin cluster%rare earths
A systematic investigation of the magnetic and transport properties of Ti doped La0.67Ca0.33MnO3 was reported. The Ti substitution for Mn ions results in a reduction in ferromagnetism and conductivity. The metal-insulator transition temperature is close to Curie temperature which decreases from 274 to 82 K as x increases from 0 to 0.17. The most important effect of Ti doping is to introduce spin clusters in the samples due to the distortion of local lattice and the inhomogeneous magnetic structure induced primarily by the random distribution of Mn ions. A maximum magnetoresistance ratio as large as 90% in 1 T at 122 K was obtained for the sample with x=0.055, which is four times larger than that obtained for LCMO sample at 272 K. There is a remarkable field-history dependent MR in the cooling process for the doped samples while such phenomenon disappears in the warming run. The resistivity follows well the variable range hopping behavior in paramagnetic state. Both the size effect and spin dependent hopping of carriers between the spin clusters should be considered in this system.