Effect of a magnetic field on the permittivity of 80%La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/20%GeO$_{2}$ composite

The dielectric properties of a magnetoresistive conducting two-phase 80%La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/20%GeO$_{2}$ (wt %) composite have been studied near the percolation threshold in magnetic fields from 0 to 15 kOe at frequencies of the measurement field from 5 kHz to 1 MHz. The samples have inductive impedances; i.e., their permittivities can be considered negative due to a high conductivity in this frequency range. The permittivity increases in magnitude in magnetic field, and the values of the magnetodielectric coefficient reach 23% at room temperature. The reasons for the effect of magnetic field on the dielectric permittivity of samples are discussed.