Directionally dependent magneto-optical response of(La0.4Pr0.6)1.2Sr1.8Mn2O7: Understanding the high-field ferromagnetic metallic state

Abstract

We investigate the polarized magneto-optical response of ${({\mathrm{La}}_{0.4}{\mathrm{Pr}}_{0.6})}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ in order to reveal the microscopic nature of the states involved in the field-induced paramagnetic semiconductor to ferromagnetic metal transition. We find significant changes in the electronic structure of the title compound under magnetic fields due to the evolution of the Jahn-Teller-split ${\mathrm{Mn}}^{3+}\phantom{\rule{0.3em}{0ex}}{e}_{g}$ orbitals. Consequences of this field-induced modification of the $d$ orbitals include the substantial colossal magnetoresistence effect, unusual magnetic relaxation behavior, and a change in orbital occupation. Based upon the directional dependence of the magneto-optical spectra, we demonstrate that the high-field ferromagnetic state is homogeneous.