Extrinsic inhomogeneity effects in magnetic, transport and magnetoresistive properties of La_{1-x}Ca_{x}MnO_{3} (x\approx 0.33) crystal prepared by the floating zone method

摘要

The paper describes a study of the magnetic, transport and magnetoresistiveproperties of La_{1-x}Ca_{x}MnO_{3} (x\approx 0.33) crystals prepared by thefloating-zone method. We found that these properties testify to rather goodcrystal perfection of the sample studied. In particular, a hugemagnetoresistance ([R(0)-R(H)]/R(H) in the field H = 5 T is about 2680 %) isfound near the Curie temperature (216 K). At the same time, some distinctfeatures of measured properties indicate the influence of extrinsicinhomogeneities arising due to technological factors in the sample preparation.Analysis of the data obtained shows that these are rare grain boundaries andtwins. Specific influence of the grain-boundary-like inhomogeneities on thetransport and magnetoresistive properties are considered.