High-temperature electron paramagnetic resonance in magnets with the Dzyaloshinskii-Moriya interaction.

We analyze the high-temperature electron paramagnetic resonance (EPR) absorption in a weakly anisotropic Heisenberg magnet having two distinct types of anisotropy, represented, respectively, by a symmetric term and the Dzyaloshinskii-Moriya (DM) term. Contrary to the widespread opinion that the latter is responsible for the excessive linewidth observed in the EPR spectra of many oxides, we prove that its contribution to the linewidth is only of the same level as that of the symmetric anisotropy. This gives a solution to the long-standing controversial problem of the high-temperature magnetic relaxation in quantum-spin systems with the DM interaction.