We report on our recent electron-tunneling studies of bulk manganite samples that provide important information about the structure of the near-surface layers of the material and the nature of the charge transport across them. It is shown that the even part of the differential conductance of contacts formed by a metallic injector with the surface of a manganite is a power function of the voltage bias. High voltages applied to the sample are found to locally modify the conductance of the degraded native surface layer. Experiments aimed to monitor the force applied to a metal tip pressed into the surface of a manganite prove the presence of sub-surface layers with properties significantly different from those near the surface. Experimental data are analyzed and interpreted within the Glazman–Matveev theory taking into account inelastic tunneling through two metallic "drops" inside the insulating barrier.
Experimental attempts to observe the elementary excitations of an orbitally ordered state (orbitons) in strongly correlated electronic systems by means of Raman scattering and by inelastic x-ray scattering are discussed for the Mott insulator LaMnO3. The results of investigations of the differential conductivity of heterostructures, consisting of a silver needle and manganite-doped La0.57Ca0.43MnO3, for voltages above the phonon and magnon frequencies of manganites are presented. Three peaks at energies corresponding to the peaks in the Raman scattering spectra of LaMnO3 are observed. It is assumed that these peaks are due to the interaction of tunneling electrons with excitations in the orbital subsystem of a degraded region adjoining the metal–manganite interface.
The results of tunneling measurements of the spectra of quasiparticle excitations of the Bose type in a nanoscale region at a surface of doped manganites immediately adjacent to a metal-oxide interface are presented. A comparison of the results with the published data for the corresponding bulk samples indicates that the properties of complex oxides of manganese near an interface are not substantially different from those in the bulk of the material. It is found that when a high voltage pulse is applied, the spectra are smoothed out and the intensity of low-frequency excitations grows on account of structural disordering of the sample in the vicinity of the interface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.