Effect of grain boundary layer strain on the magnetic and transport properties of (100−x) La0.7Ca0.3MnO3/(x) BaTiO3 composites showing enhanced magnetoresistance

A ferromagnetic/ferroelectric composite system, viz. (100−x)La0.7Ca0.3 MnO3 [LCMO]/(x) BaTiO3 [BTO] (with x=0.0%, 1.0%, 5.0%, 7.5%, 10.0% and 15.0%, in wt%) has been synthesized and the temperature-dependent DC magnetization M(T), resistivity ρ(T), magnetoresistance (MR), and thermoelectric power S(T) have been studied. Both metal–insulator transition temperature (TMI) and the corresponding Curie temperature (TC) decrease whereas peak resistivity at TMI increases as x is enhanced from 0.0% to 10.0%. For x>10.0%, this trend of variation is reversed. A maximum three-fold increase of magnetoresistance (MR) is observed (for sample with x=10.0%) due to the addition of ferroelectric (non-magnetic) perovskite BTO (compared to the mother compound LCMO). Interestingly, thermoelectric power S(T) shows a pronounced depression (dip) near the magnetic transition region for the composite samples. The above results have been analyzed considering strain induced by the LCMO/BTO grain boundary layer (BL).