Pressure effects on the metal-insulator transition in magnetoresistive manganese perovskites

Abstract

Quasi-hydrostatic-pressure measurements of electrical resistivity up to 11 kbar are presented for a series of manganese perovskites ${L}_{2/3}{A}_{1/3}{\mathrm{MnO}}_{3}.$ It is found that the Curie temperature ${T}_{C},$ being itself a function of the electronic bandwidth $W,$ displays a larger variation of $d\mathrm{ln}{T}_{C}/dP$ as the bandwidth is reduced. It is shown that this effect arises primarily from the Mn-O-Mn bond stretching under pressure. However, the observed $d\mathrm{ln}{T}_{C}/dP$ versus ${T}_{C}$ or $W$ variations are found to be significantly larger than expected on the basis of simple steric modifications of bandwidth. We suggest that the electron-phonon coupling is substantially reduced under pressure; this effect is more prominent as the bandwidth is reduced.