Point-contact spectroscopy of single crystal La_0.75Sr_0.25MnO₃ and resistivity due to electron-phonon interaction

Abstract

In this paper we report point-contact spectroscopy (PCS) measurements on single crystals of metallic La_0.75Sr_0.25MnO₃. The electron-phonon coupling function as obtained from the PCS shows large peaks for phonon frequencies 20 meV<∼ω<∼100 meV. This leads to a rather large electron-phonon coupling constant λ≃1.2. We have shown that a sizable fraction of the total resistivity in the temperature range T<∼0.4T_c can be of phononic origin and can be explained using the experimentally observed electron-phonon coupling function. As T^→T_c, extra contribution to resistivity arising from spins dominate. We find that the magnetoresistance vanishes in the temperature range T<∼0.4T_c, where the predominant contribution to ρ arises from phonons. We have also performed PCS in 6 T magnetic field. The resistivity calculated from the spectrum at 6 T does not differ appreciably from that calculated at 0 T. Our experiment has been validated by a similar experiment on a nonmagnetic perovskite oxide system, Na_0.9WO₃.