Negative dynamic dielectric permittivity of a ceramic multiferroic LuFe$_{2}$O$_{4}$ with oxygen nonstoichiometry under the combined influence of temperature and electric field

The temperature dependences (100 – 380 K) of the dielectric constant and conductivity of a ceramic multiferroic LuFe$_{2}$O$_{4}$ with oxygen nonstoichiometry, measured at alternating current (1, 10, 100 kHz, 1 MHz) and in a static electric field (0 – 8 V/1.4 mm), are presented. The regularity of the sign inversion of the dynamic permittivity caused by the appearance of solid-state inductance in the samples is discussed.