Finite size effects in the Verwey transition of magnetite thin films
  We report on the finite size effects in the Verwey transition of stress-free magnetite Fe3O4 thin films. A limit thickness of 20 nm is evidenced, above which the transition temperature TV is constant and close to 120 K (bulk value) and below which no genuine transition is observed. Field Cooled and Zero Field Cooled measurements evidence irreversibilities for all thicknesses. This irreversible behavior abruptly disappears around TV for the thicker films, when the magnetic anisotropy vanishes. These behaviors are interpreted in terms of assemblies of interacting magnetic Fe3O4 clusters, which are smaller than the antiphase domains present in the films. 
Alexandre Bataille (SPCSI), Eric Vincent (SPEC), Susana Gota (SPCSI),   Martine Gautier-Soyer (SPCSI)