55Mn nuclear magnetic resonance for antiferromagnetic α-Mn2O3

Abstract

The zero-field Mn-55 nuclear magnetic resonance (NMR) spectra for antiferromagnetic alpha-Mn2O3 were obtained at low temperatures. The Gaussian-shaped spectrum was positioned around 314 MHz in the zero-temperature limit, and the linewidth was about 5 MHz. The magnetic moment estimated from the resonance frequency was 2.6 mu(B) per Mn3+ ion, which corresponds to 65% of 4 mu(B), which is expected when only the contribution of spin to the magnetic moment is considered. The temperature dependence of the sublattice magnetization does not fit Bloch's T-2 law well but instead fits the exponential form applicable when there is an initial energy gap in the dispersion relation of the spin wave. From the fitting, we obtained an energy gap of 1.82 meV and an anisotropy energy of 0.22 meV. The spin-spin relaxation time measured as a function of frequency shows that the Suhl-Nakamura interaction is suppressed by this energy gap. The line broadening is mostly influenced by the dipolar hyperfine interaction.