Enhanced room-temperature magnetoresistance in high-temperature sintered La2/3Sr1/3MnO3 doped with ZrO2

Granular metal/insulator (La2/3Sr1/3MnO3 doped with ZrO2) composites were prepared by high-temperature sintering. The effects of sintered time on structure and grain size, as well as on magnetic and electric properties have been investigated. The XRD patterns of all doped samples show that the crystal structure is predominantly a perovskite phase with R3¯c symmetry, in addition to the minor secondary compounds (SrZrO3, La2Zr2O7 and ZrO2). The microscopic studies show that the long-time sintered samples have excellent connectivity between grains. The analysis of XPS reveals that the loss of oxygen occurs during the high-temperature sintering in air. It is also found that with sintered time increasing the paramagnetic insulator–ferromagnetic metal transition temperature TC (or TP) decreases gradually and the room-temperature magnetoresistance increases significantly.