Microwave Response of La_(2/3)Ca_(1/3)MnO_3 Thin Films

摘要

The investigations of microwave (MW) response of both epitaxial and polycrystalline La_(0.67)Ca_(0.33)MnO_3 (LCMO) thin films, magnetron sputtered onto lattice matched NdGaO_3(100) and MgO(100) substrates, respectively, are presented. Both the MW radiation induced anomalous resistance increase and fast resistance relaxation observed in this work for epitaxial LCMO film just below the paramagnetic (PM) to ferromagnetic (FM) transition temperature T_c demonstrate a clear evidence of dynamical phase coexistence in the material. Similar investigations of LCMO/MgO films exhibited the importance of intergrain boundaries on the high frequency conductivity of polycrystalline material. The MW response of the films, both below and above T_c, has been explained assuming influence of strong microwave radiation on the hopping conductance of high resistance intergrain material.