New low-frequency magnetic excitations in LaMnO₃ single crystals

Abstract

Microwave magnetic resonance of close to stoichiometric antiferromagnetic LaMnO_{3 − δ} was investigated. LaMnO_{3 − δ} single crystals were grown and a series of samples with a small oxygen excess and deficiency was prepared. Residual magnetization was observed for all samples in the series. The maximum value of the residual magnetic moment in the series of samples obtained was 2.5% of the maximum possible value (4_μB for each Mn ion). An absorption line, whose angular and frequency dependences cannot be explained on the basis of a previously proposed [S. Mitsudo, et al., J. Magn. Magn. Mater. 177–181, 877 (1998)] model of two-sublattice antiferromagnet with “easy axis” magnetic anisotropy (∥ b) and canting of the magnetic sublattices due to the Dzyaloshinski$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}$-Moriya interaction, was observed in the experiments performed on all samples in a series as well as on specially prepared ceramic samples with the same composition. It was inferred that the low-frequency excitations in a system of ferromagnetic drops observed in [M. Hennion, et al., Phys. Rev. Lett. 81, 1957 (1998)] are observed in the experiment.