Observation of C-type orbital ordered phase and orbital flipping in LaVO3

The orthovanadate system RVO3 (R = rare-earth and Y) is known to exhibit multiple orbital, magnetic, and structural transitions depending on the size of the rare-earth ions. LaVO3 is reported to exhibit a G-type orbital ordered (G-OO) phase and magnetization reversal below the antiferromagnetic transition. From high angular resolution synchrotron x-ray powder diffraction measurements, we report the observation of the C-OO phase, hitherto unknown in LaVO3, and its coexistence with the G-OO phase below T1OO (-135 and 125 K) in ambient pressure (AP) and high-pressure (HP) synthesized LaVO3, respectively. At T2OO- 20 K, HP-LaVO3 shows an orbital flipping transition from G- to C-OO, which results in an increase of the C-OO phase fraction. At 6 K, the C-OO phase becomes predominant (-61%) in HP-LaVO3, whereas it is -41% in AP-LaVO3. We suggest that the different magnetic structures associated with coexisting orbital ordered phases should be responsible for the magnetization reversal phenomenon in LaVO3.