Spin dynamics in La_{1-x}Sr_{x}MnO_{3} (x \le 0.175) investigated by high-field ESR spectroscopy

TL;DR

This study uses high-field ESR spectroscopy to investigate the spin dynamics and magnetic phase transitions in La_{1-x}Sr_xMnO_3 crystals across various doping levels, revealing complex magnetic behaviors and transitions.

Contribution

It provides detailed high-frequency ESR data on La_{1-x}Sr_xMnO_3, identifying magnetic phase changes and canted structures with doping, which were not previously characterized at this level.

Findings

Observation of AFMR mode splitting in parent LaMnO_3.

Detection of abrupt changes in AFMR frequencies around x=0.025.

Identification of ferromagnetic and metallic states at higher doping levels.

Abstract

High-field electron spin resonance (ESR) experiments have been carried out in single crystals of La_{1-x}Sr_xMnO_3 in the concentration range 0 \le x \le 0.175. Different quasioptical arrangements have been utilized in the frequency range 40 < \nu < 700GHz and for magnetic fields B \le 12T. A splitting of the antiferromagnetic resonance (AFMR) mode is observed in the magnetic field for the parent compound LaMnO_3 in agreement with the antiferromagnetic structure of this material. Abrupt changes in the AFMR frequencies have been observed around x = 0.025 and attributed to the possible transition between antiferromagnetic and canted state. For increasing Sr-doping the observed AFMR modes are splitted even in zero field, which can be naturally explained using a concept of a canted magnetic structure for x<0.1. In La_{0.825}Sr_{0.175}MnO_3 the ESR spectra are consistent with the ferromagnetic and metallic state. The lines of ferromagnetic resonance and ferromagnetic antiresonance can be clearly seen in the spectra. For intermediate concentrations 0.1 \le x \le 0.15 a complicated set of ESR spectra has been observed, which can be well explained by a single ferromagnetic resonance mode and taking into account electrodynamic effects.