Spin order in FeV₂O₄ determined by single crystal Mössbauer spectroscopy in applied magnetic field

In order to clarify the spin order of FeV₂O₄, ⁵⁷Fe Mössbauer spectroscopy has been conducted by using a single crystal specimen. A measurement in applied magnetic field has been also conducted. By applying a slight compression in the sample plane, almost single domain state was achieved in the low temperature phases. The spectra consist of Fe²⁺ spectra (~ 85%) and Fe^2.5+ spectra (~ 15%), corresponding to the A- and B-site Fe ions, respectively. The B-site spectrum well represents the local structure and the magnetic structure of V³⁺ ion on the B-site. Notable changes in the Mössbauer parameters are recognized at 140, 110, and 65 K, where the successive phase transitions take place. The feature well represents the orbital and spin order. In the orthorhombic phase below 110 K, Fe²⁺ and V³⁺ spins form a collinear ferrimagnetic order along the a-axis. Below 65 K in the low temperature tetragonal phase, however, both spins incline from the c-axis to form a canted ferrimagnetic structure. The canting angles are about 17° and 52° at 4.2 K for Fe²⁺ and V³⁺ spins, respectively.