Structural Change on the Magnetic Field-Induced Insulator-to-Metal Transition in Distorted Perovskite Eu_0.6Sr_0.4MnO₃

Abstract

Structural feature of Eu_0.6Sr_0.4MnO₃ through the magnetic-field-induced insulator-to-metal (IM) transition has been investigated by X-ray powder diffraction in a magnetic field using synchrotron radiation. No superlattice reflections due to the charge and orbital ordering are detected in the insulator phase down to 20 K. Both of the insulator phase and the induced metal phase are proved to be in orthorhombic structure with Pnma space group, and thus a change of the crystal symmetry is not detected on the IM transition. However, the lattice constants abruptly increase and the reflection intensities abruptly change through the transition. These suggest a rotation of MnO₆ octahedron in a manner to increase Mn–O–Mn angles. This structural change is consistent with a gain in electron transfer energy in the double exchange mechanism that stabilizes the metallic and ferromagnetic state.