Sublattice Magnetization of FeBO3Single Crystals by Mössbauer Effect

Mössbauer-effect (ME) measurements of the hyperfine interaction of the iron nuclei in single crystals of FeB${\mathrm{O}}_3$ have been used to study the temperature dependence of the sublattice magnetization. The results are found to be consistent with previously published nuclear-magnetic-resonance results and agree quantitatively with simple noninteracting-spin-wave theory for $T\le \frac{T_N}{3}$, where $T_N$ is the Néel temperature. The exchange integral calculated from fitting ME data to spin-wave theory, $J=27.3\mathrm{}\pm 0.5$ °K, is in very good agreement with that calculated from the Rushbrooke and Wood $T_N$ relation, indicating that FeB${\mathrm{O}}_3$ is very dominantly a nearest-neighbor-exchange system. We estimate that the upper spin-wave branch (out plane) has a gap of about 23 °K, which is primarily due to dipolar anisotropy but partly to the Dzyaloshinskii-Moriya field.