Particle-size effects on the value of T_c of MnFe₂O₄: evidence for finite-size scaling

Abstract

⁵⁷Fe Mössbauer measurements show that the T_c of <12>-nm particles of MnFe₂O₄ is higher than that of the <33>-nm particles, which exhibit the bulk T_c value (573 K). The ⁵⁷Fe isomer shift as well as the internal field are, however, independent of the particle size, as is the cation distribution determined by Mn and Fe extended X-ray absorption fine structure and Mn X-ray absorption near-edge structure measurements at different temperatures. The results confirm that the higher T_c of the <12>-nm particles arises from finite-size scaling.