Photoinduced Demagnetization and Insulator-to-Metal Transition: Analyzing Ferromagnetic Insulating BaFeO_3 Thin Films

摘要

Control of magnetic states by optical excitations in magnetically ordered materials has attracted considerable attention since the demonstration of ultrafast demagnetization in Ni within 1 ps, explored by time-resolved magneto-optical Kerr effect studies by Beaurepaire et al. [1]. They proposed a phenomenological "three-temperature model" in order to understand the ultrafast demagnetization, which considers three interacting reservoirs of electrons, spins, and lattice, and suggested the importance of direct electron-spin interactions. Here we report on pump-probe time-resolved resonant x-ray reflectivity study of fully oxidized single crystalline BaFeO_3 thin films [2], which show unusual behaviors of ferromagnetic and insulating properties with saturation magnetization and a Curie temperature of 3.2 μB/formula unit and 115 K, respectively [3,4]. The investigation of the demagnetization dynamics of insulators allows one to relate electronic structure to magnetic dynamics.