Stability of Jahn-Teller distortion in LaMnO3 under pressure:: An X-ray absorption study

The local environment of manganese atoms in LaMnO3 under pressure up to 15.3 GPa has been studied by x-ray absorption spectroscopy. For pressures below 8 GPa, no change is detected within the MnO6 octahedra. Above this pressure a continuous reduction of the long Mn-O distance takes place, however, the octahedral distortion persists over the whole pressure range. At 15.3 GPa the average Jahn-Teller splitting of the distances is reduced by about one-third, indicating that a total removal of the local Jahn-Teller distortion would occur only for pressures around 30 GPa, where metallization is reported to take place. A hysteresis in the long distance reduction is observed down to ambient pressure, suggesting the coexistence of MnO6 distorted and undistorted units.