Electrical transport and magnetic properties of [formula omitted] composite ceramics

Abstract

A cuprate/manganite composite ceramic, viz. (La0.7Ca0.3MnO3)1−x(Y1Ba2Cu3O7−δ)x with x=0, 0.10, 0.20, 0.30, and 0.50 has been synthesized, and the dc magnetization, the resistivity, and the magnetoresistance (MR) have been studied. The composite ceramic is identified as a two-phase composite consisting of ferromagnetic manganite and superconductor by x-ray diffraction and scanning electron microscopy. The temperature dependence of resistivity between 10 and 300K shows that the transport behavior of the composite ceramic is governed by grain boundaries. With increasing the YBCO doping content, the positive MR of YBCO phase dominates the negative MR of LCMO one, which gives rise to the enhancement of magnetic inhomogeneity and the suppression of double exchange interaction. The sign of MR for the composite ceramic is observed to be dependent on magnetic field and the YBCO doping content. The tuning between positive and negative MR by means of magnetic field can be developed to be the field-sensitive tunable MR. The tunable MR is due to the coexistence of positive and negative MR, which is affected by the proximity effect between LCMO and YBCO phases below TC.