High-pressure synthesis,structure and magnetic properties of LaCrO3 ceramics

Single-phase LaCrO₃ ceramics was synthesized successfully by the solid state sintering method under high pressure (5 GPa). X-ray diffraction measurements suggest that the high-pressure synthesized sample is well-crystallized, but the cell volume is larger than that of the sample synthesized under ambient pressure, which can be ascribed to the occurrence of Cr²⁺ converted form part of Cr³⁺. Such mixed valent state with coexistence of Cr²⁺ and Cr³⁺ could be confirmed by X-ray photoelectron spectroscopy measurements. Magnetic measurement results indicate that in addition to antiferromagnetic superexchange interaction of Cr³⁺-O-Cr³⁺ network accompanied by weak ferromagnetism at high temperature, another kind of ferromagnetic behavior can be observed at low temperature (below 30 K), which could be attributed to double exchange interaction of Cr²⁺-O-Cr³⁺ networks.