Magnetoresistance of Polycrystalline La$\text{}_{0.7}$Ca$\text{}_{0.3}$MnO$\text{}_{3}$ Films in a Microwave Magnetic Field

We present new experimental evidence indicating the importance of magnetic field component of microwave field (f=9.4 GHz) for magnetoresistive properties of polycrystalline La$\text{}_{0.7}$Ca$\text{}_{0.3}$MnO$\text{}_{3}$ films. The microwave measurements revealed a different character of the temperature-dependent electrical resistance of polycrystalline La$\text{}_{0.7}$Ca$\text{}_{0.3}$MnO$\text{}_{3}$ films placed in the centre (maximal amplitude of H$\text{}_{10}$ wave vector) and at a narrow wall of the wave-guide (reduced H$\text{}_{10}$ amplitude). Theoretical estimations of the influence of substrate onto distribution of microwave electric and magnetic fields in the waveguide were performed using the finite-difference time-domain method.