Thermomagnetic irreversibility and magnetic short range ordering in Mn2.5Co0.5O4 tetragonal spinel thin films.

Mn2.5Co0.5O4 films are grown on MgO(001) and (011) substrate by molecular beam epitaxy. Detailed structural and magnetic analyses are carried out by x-ray diffraction and magnetization measurements. The reduction of the lattice parameter c/a* ratio and the enhancement of the Curie temperature (from 43 to 66 K), due to the weakening of the Jahn-Teller effect, are observed. In addition, thermomagnetic reversibility is observed at lower temperature and low external filed indicating the existence of local canting states. The randomness of Co cation and uniaxial anisotropy further enhance the local canting effect. An H-T phase diagram is mapped out, which indicates a short rang order state in the temperature 66-85 K separating the ferrimagentic and paramagnetic phases. [ABSTRACT FROM AUTHOR]