Temperature Dependence of the Sublattice Magnetization in Ferrimagnetic MnFe2O4

Abstract

The temperature dependence of the A‐site sublattice magnetization in ferrimagnetic MnFe₂O₄ has been measured by observing the temperature dependence of the Mn⁵⁵ NMR frequency. The initial deviation from saturation is proportional to $T^{\frac{3}{2}}$ but no $T^{\frac{5}{2}}$ term is observed. These results are found in agreement with a ferrimagnetic spin‐wave calculation for the spinel lattice. Two $T^{\frac{5}{2}}$ terms of opposite sign originate from the k⁴ terms of the dispersion relation and the k‐dependent transformation coefficients from single sublattice spin‐deviation operators to the diagonal spin‐wave variables. These two terms cancel, for the spinel lattice, to within 1%.