Microwave studies of thin manganite films on SrTiO3 substrate

We report phase-sensitive microwave studies of thin epitaxial manganite La1−xSrxMnO3 films on SrTiO3 substrate. The measurements were performed in the temperature range of 80–330K using a contactless microwave scanning probe operating at 26GHz with the aim of comparing dc resistivity and microwave resistivity. We find that the dc and the microwave resistivity of the La0.8Sr0.2MnO3 are almost the same, while for the La0.7Sr0.3MnO3 they are different above 200K. Our analysis of different mechanisms of this discrepancy, together with our measurement of the ferromagnetic resonance on the same samples, yields the film inhomogeneity on the microscopic scale as the most probable explanation.