High-frequency dielectric study of multiferroic Bi0.9La0.1Fe0.9Mn{0.1}O3 thin films

La- and Mn-doped multiferroic BiFeO₃ thin films were fabricated and characterized at radio- and microwave frequencies using the parallel-plate capacitor structures at a room temperature. A single phase epitaxial-quality thin films were grown by RF sputtering on SrTiO₃(100) substrate with highly conductive SrRuO₃ and Ti/Au layers used as bottom and top electrodes. In the frequency range 40 MHz - 30 GHz the Bi_0.9La_0.1Fe_0.9Mn_0.1O₃ (BLFMO) films show relatively low losses and dielectric constant value close to 90. Analysis of the frequency dependences of loss tangent shows power law ^1/3 with estimated value of microwave loss tangent less than 0.06 at frequencies below 20 GHz. We assume that the oxygen vacancies in the thin film act as charged defects and cause extrinsic microwave losses.