Bandwidth-driven nature of the pressure-induced metal state of LaMnO₃

¹ Institut Néel, CNRS et Université Joseph Fourier - BP 166, F-38042 Grenoble Cedex 9, France, EU
² Advanced Photon Source, Argonne National Laboratory - Argonne, IL 60439, USA
³ Laboratório Nacional de Luz Síncrotron - P.O. Box 6192, 13084-971, Campinas, São Paulo, Brazil
⁴ Synchrotron SOLEIL - L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex, France, EU
⁵ Centro Atómico Bariloche, CNEA and Universidad Nacional de Cuyo - 8400 S.C. de Bariloche, Argentina

^a aline.ramos@grenoble.cnrs.fr

Received: 11 July 2011
Accepted: 8 August 2011

Abstract

Using X-ray absorption spectroscopy (XAS), we studied the local structure in LaMnO₃ under applied pressure across and well above the insulator-to-metal (IM) transition. A hysteretic behavior points to the coexistence of two phases within a large pressure range (7 to 25 GPa). The ambient phase with highly Jahn-Teller (JT) distorted MnO₆ octahedra is progressively substituted by a new phase with less-distorted JT MnO₆ units. The electronic delocalization leading to the IM transition is finger-printed from the pre-edge XAS structure around 30 GPa. We observed that the phase transition takes place without any significant reduction of the JT distortion. This entails band overlap as the driving mechanism of the IM transition.