Origin of elevated ordering temperature in MnFe2O4 nanometer particles

Mossbauer spectra of MnFe2O4 with various particle sizes in a longitudinal 50 kOe magnetic field show that the Fe ion occupancy of the A and B crystallographic sites depends on the particle size. The elevated Neel temperatures with decreasing particle sizes are attributed to an increased iron occupancy on the A sites; this in turn leads to an increase in the total superexchange interaction.