Dzyaloshinsky-Moriya interaction and field-induced magnetic order in an antiferromagnetic honeycomb lattice compound Bi3Mn4O12(NO3) studied by high-field electron spin resonance

Abstract

High-field electron spin resonance (ESR) measurements of ${\mathrm{Bi}}_{3}{\mathrm{Mn}}_{4}{\mathrm{O}}_{12}({\mathrm{NO}}_{3})$, which has been suggested recently as a new honeycomb lattice antiferromagnet with spin frustration, have been performed in a field region up to 20 T. An ESR measurement at 265 K shows an isotropic broad resonance, and the obtained $g$ value is $1.974\ifmmode\pm\else\textpm\fi{}0.016$, which is consistent with the ${\mathrm{Mn}}^{4+}$ ion in a crystal field with low symmetry. At 1.8 K, resonances, whose frequency-field relation corresponds to antiferromagnetic resonance (AFMR) with an easy-plane type anisotropy and a Dzyaloshinsky-Moriya (DM) interaction, appear above 6 T. This result is consistent with the field-induced magnetic order (FIMO) phase suggested by a previous neutron measurement. From the analysis of our AFMR result, the $D$ term of the DM interaction is estimated as 1.3 K, and the direction of the $D$ term is suggested to be along the $c$ axis, which is consistent with the crystal symmetry. Using this $D$ and the exchange interaction, the canted angle is estimated to be 2.42${}^{\ensuremath{\circ}}$, which can interpret the magnetization jump at the metamagnetic transition qualitatively. The possible origin of the FIMO phase is discussed with recent theoretical results within the ${J}_{1}\ensuremath{-}{J}_{2}$ model.