Stability of the Jahn-Teller effect and magnetic study of LaMnO3 under pressure - art. no. 064426

We have studied the crystal structure of LaMnO3 under pressure up to 80 kba r at room temperature by TOF neutron diffraction. The analysis of the cryst al structure as a function of pressure has revealed that the Jahn-Teller (J T) distortion is stable up to about 70 kbar. The contraction of the MnO6 oc tahedra is nearly isotropic, but the average tilt angle diminishes with inc reasing pressure. This behavior shows that LaMnO3 evolves towards a wider e lectronic band system. Above 70 kbar the compound undergoes a transition to an unknown phase. This transition is probably due to the suppression of,th e Jahn-Teller effect because of the closing of the JT gap: the ionic Mn3+ s pecies disappear and the system evolves towards a metalliclike phase. At lo w temperature the effect of the applied pressure is first to increase the t ransition temperature and second to suppress magnetic ordering when the met alliclike phase is reached.