Directionally dependent magneto-optical response of (La_(0.4)Pr_(0.6))_(1.2)Sr_(1.8)Mn_2O_7: Understanding the high-field ferromagnetic metallic state

摘要

We investigate the polarized magneto-optical response of (La_(0.4)Pr_(0.6))_(1.2)Sr_(1.8)Mn_2O_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 Mn~(3+) 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.