Microwave studies of thin manganite films on SrTiO3 substrate

Abstract

Colossal magnetoresistive La 0.7 ( Pb 1−x Sr x ) 0.3 MnO 3 films for bolometer and magnetic sensor applicationsWe report phase-sensitive microwave studies of thin epitaxial manganite La 1−x Sr x MnO 3 films on SrTiO 3 substrate. The measurements were performed in the temperature range of 80-330 K using a contactless microwave scanning probe operating at 26 GHz with the aim of comparing dc resistivity and microwave resistivity. We find that the dc and the microwave resistivity of the La 0.8 Sr 0.2 MnO 3 are almost the same, while for the La 0.7 Sr 0.3 MnO 3 they are different above 200 K. 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.

Appearance of an inhomogeneous superconducting state in La0.67Sr0.33MnO3-YBa2Cu3O7-La0.67Sr0.33MnO3 trilayers

“…Figure 2 also shows the variation of exchange energy (E ex ) extracted from the M (T ) data of figure 1 with d F . The calculated value of E ex in the thick limit (∼2 meV) is in good agreement with the results obtained directly from ferromagnetic resonance measurements on similar films [28]. The decay of T c with d F in figure 2 is primarily monotonic except for the appearance of a plateau in the neighborhood of d F ∼ 450Å.…”

Low-field microwave absorption in epitaxial La0.7Sr0.3MnO3films

“…While the dominant contribution in bulk manganites arises from magnetoimpedance [14,34] there are many observations of the low-field microwave absorption in thin films that can't be explained in this way. Some of these observations were attributed to magnetoresistance in the magnetically-unsaturated state [8,35,36] while the origin of others [14,32,37,38] is unclear.…”

Spin-wave resonances inLa0.7Sr0.3MnO3films: Measurement of spin-wave stiffness and anisotropy field

“…We measured magnetization and resistivity of these films by SQUID magnetometry and four-point technique, correspondingly. The skin-depth at 9.4 GHz estimated from our resistivity measurements [23] -22 µm at 295 K and 5 µm at 50 K-considerably exceeds the film thickness.…”

“…The asymmetry arises from the coupling to the dielectric resonances in the STO substrate and was observed in other studies as well. [20,23] The angular dependence of the resonant fields (not shown here) follows Eq. (5), hence we attribute these peaks to the spin-wave resonances.…”