High-field ESR spectroscopy of the spin dynamics in La1-xSrxMnO3 (x≤0.175) -: art. no. 214422

High-field electron-spin-resonance (ESR) experiments have been carried out in single crystals of La1-xSrxMnO3 in the concentration range 0less than or equal toxless than or equal to0.175. Different quasioptical arrangements have been utilized for frequencies 40less than or equal tonuless than or equal to700 GHz and for magnetic fields Bless than or equal to12 T. A splitting of the antiferromagnetic resonance (AFMR) mode is observed in the magnetic field for the parent compound LaMnO3, in agreement with the antiferromagnetic structure of this material. Abrupt changes in the AFMR frequencies have been observed around xsimilar or equal to0.025, and were attributed to a transition between a pure antiferromagnetic and a canted state. For increasing Sr doping the observed AFMR modes are split even in a zero field, which can be naturally explained using a concept of a canted magnetic structure for x<0.1. In La0.825Sr0.175MnO3 the ESR spectra are consistent with the ferromagnetic and metallic state. The lines of ferromagnetic resonance and ferromagnetic antiresonance can be clearly observed. For intermediate concentrations 0.1 <= x <= 0.15 complicated ESR spectra were observed, which can be well explained by a single ferromagnetic resonance mode and taking electrodynamic effects into account.