Magnetoresistive and magnetocaloric response of manganite/insulator system

In this work, we have studied structural, electro-magnetic and magnetocaloric properties of La0.7Ba0.3MnO3/xTiO2 manganite/insulator system with 0 ≤ x ≤ 0.08. X-ray diffraction (XRD) shows the coexistence of TiO2 and La0.7Ba0.3MnO3 phases in doped composites through their characteristic peaks. This reveals their interaction lack preserving the R-3c rhombohedral structure for all composites. Due to interaction lack, TiO2 is suggested to segregate at grain boundaries weakening grains connectivity and decreasing metal-semiconductor transition temperature (Tms). The segregated TiO2 hinders conduction between grains leading to carriers tunneling that increases the low field magnetoresistance (LFMR) of La0.7Ba0.3MnO3 from −3% to −3.3, −3.5 and −3.7% for x = 0.02, 0.04 and 0.06 for doped composites. The dc magnetization measurements reveal the constant value of Curie temperature (Tc) and its non impact by doping level referring to the TiO2-La0.7Ba0.3MnO3 interaction lack. Also, the magnetocaloric properties of La0.7Ba0.3MnO3 are enhanced with TiO2 doping, where, the relative cooling power (RCP) of La0.7Ba0.3MnO3 has been enhanced from 35 J/kg to 51, 47, 49 and 50 J/kg for x = 0.02, 0.04, 0.06 and 0.08 composites at 1.5T magnetic field.