Magnetoresistance and transport properties of (LSMO)(1−x) –(SBT)(x) (x = 0.0, 0.13, 0.23) composite thin films on silicon substrate

Abstract

0–3 manganite-rich composite thin film composed of (1 − x) La0.67Sr0.33MnO3 + (x) SrBi2Ta2O9 with x = 0.0, 0.13, 0.23 (abbreviated as LSMO-SBTx) was fabricated by pulsed laser deposition on silicon substrate. The microstructure, electrical, magnetoresistive (MR) and transport properties of the composites were investigated systematically. X-ray diffraction and cross-sectional microstructural studies of LSMO-SBTx samples prove the presence of both LSMO and SBT phases with SBT grains embedded in the LSMO matrix. SBT grains are seen surrounded and covered by LSMO grains making it a 0–3 composite. The incorporation of the insulating ferroelectric SBT phase leads to a substantial increase in resistivity of the composites. Temperature-dependent resistivity measurement showed a shift of the peak Tp (or TM-I) from 200 to 114 K with the increase in the ferroelectric phase. Three conduction models were explored to describe the transport behaviors in different temperature regions. The dominant electron transport mechanism above TM-I has been found to be variable range hopping for Tp < T < θD/2, where θD is the Debye temperature, and the adiabatic small polaronic model for T > θD/2. Since the films were of high disorder, the electron–electron and electron–phonon scatterings have been found to play the dominant role in deciding the resistivity at low temperatures. A comparison between the MR plot for the three samples at 100 K found the LFMR peak to be present in both the LSMO-SBT0.13 and LSMO-SBT0.23 samples, but absent for the LSMO-SBT0 sample. At a temperature of 10 K and at a field of 6 kOe, the MR value was 6%, 12%, and 16% for LSMO-SBT0, LSMO-SBT0.13, and LSMO-SBT0.23, respectively.