Enhanced magnetic moment in ultrathin Fe-doped CoFe2O4 films

Article

关键词: FERRITE THIN-FILMS;    TRANSITION-METAL COMPOUNDS;    COBALT FERRITE;    SUBSTITUTED MAGNETITE;    ABSORPTION-SPECTRA;    ANISOTROPY;    ORIGIN;    SPINTRONICS;    BEHAVIOR;    FE3O4;   

DOI  :  10.1103/PhysRevB.86.174404

来源: SCIE

【 摘 要 】

The effect of film thickness on the magnetic properties of ultrathin Fe-doped cobalt ferrite (Co1-xFe2+xO4) grown on MgO (001) substrates is investigated by superconducting quantum interference device magnetometry and x-ray magnetic linear dichroism, while the distribution of the Co2+ cations between the octahedral and tetrahedral lattice sites is studied with x-ray absorption spectroscopy. For films thinner than 10 nm, there is a large enhancement of the magnetic moment; conversely, the remanent magnetization and coercive fields both decrease, while the magnetic spin axes of all the cations become less aligned with the [001] crystal direction. In particular, at 300 K the coercive fields of the thinnest films vanish. The spectroscopy data show that no changes occur in the cation distribution as a function of film thickness, ruling this out as the origin of the enhanced magnetic moment. However, the magnetic measurements all support the possibility that these ultrathin Fe-doped CoFe2O4 films are transitioning into a superparamagnetic state, as has been seen in ultrathin Fe3O4. A weakening of the magnetic interactions at the antiphase boundaries, leading tomagnetically independent domains within the film, could explain the enhanced magnetic moment in ultrathin Fe-doped CoFe2O4 and the onset of superparamagnetism at room temperature.

【 授权许可】

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