Improvement of magnetoresistance over a wide temperature range in La_2/3Sr_1/3MnO₃/polymer composites

Abstract

Polymer-embedded La2/3Sr1/3MnO3 (LSMO) composites, (LSMO)1 −x(PPP)x (PPP is polyparaphenylene, and x is the weight fraction of PPP), were prepared by mixing pre-prepared LSMO and PPP powders. Thermogravimetric analysis, x-ray diffraction, and infrared spectra show that the composites are stable when calcined at 400oC. Significant enhancement in the magnetoresistance (MR) effect over a wide temperature range is observed for the composites compared with the parent LSMO. The MR enhancement reaches its maximum at x = 0.2. The magnetotransport is mainly attributed to intergrain spin-polarized tunnelling. We argue that the introduction of PPP gives rise to magnetic disorder and hence an enhanced tunnelling effect, which is responsible for the MR enhancement.