Barrier and self-energy effects in manganite tunneling characteristics

Tunneling conductance spectra of point-contact junctions formed by sharp Ag tip and two optimally doped manganites La0.67Sr0.33MnO3 and Nd0.67Sr0.33MnO3 are measured and analyzed. It was found that analytical dependence of the different conductance on voltage strongly depends on the bias sign and dramatically changes after voltage treatments. The data obtained are explained in terms of the Glasman-Matveev model for tunneling across two localized states settled in the barrier near the manganite bulk. Effective functions of boson-electron interactions extracted from self-energy contributions to the experimental characteristics contain signs of phonon and magnon excitations, higher-energy satellites as a results in the near-barrier region in the form of strong not-well reproduced peaks. (author)