Magnetic, dielectric, and transport properties of La1−xSrxMnO3 at submillimeter wavelengths

Abstract

Antiferromagnetic resonance (AFMR), dynamic conductivity, and dielectric permittivity have been studied in the La1−xSrxMnO3 perovskites at a frequency range of ν=3–33 cm−1 by the use of a quasi-optical backward-wave-oscillator technique. Two AFMR modes have been observed in LaMnO3 and La0.95Sr0.05MnO3. Temperature dependencies of their resonance frequencies, linewidths, and mode contributions to a static magnetic permeability have been obtained and corresponding parameters of magnetic interactions have been extracted. A jump in the dielectric permittivity ε′(T) was found at T=100–120 K in La0.9Sr0.1MnO3, which indicates the existence of an additional phase transition (probably, a polaron ordering) besides the ferromagnetic transition at 170 K. A sharp increase of the dynamic conductivity σ′(ν,T) was observed near Curie temperature (285 K) at a metal–semiconductor transition in La0.825Sr0.175MnO3, which was slightly smaller than its static value.