Pressure-induced insulator-metal transition in a bilayer manganite: Pressure control of orbital stability

Abstract

Pressure effects on transport as well as structural properties have been investigated for a bilayer manganite, ${\mathrm{La}}_{2\ensuremath{-}2x}{\mathrm{Sr}}_{1+2x}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ $(x=0.48),$ near the phase boundary between the ferromagnetic metallic and the A-type antiferromagnetic states. An insulator-metal (IM) transition is found to be induced by applying pressure of $\ensuremath{\sim}0.7 \mathrm{GPa}.$ On the basis of the synchrotron radiation x-ray structural analysis under high pressures, we have ascribed the IM transition to the variation of the stability of the ${e}_{g}$ orbitals.