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The hard magnetic properties of Fe3Se4 nanostructures were studied both experimentally and theoretically. Magnetic measurements showed that Fe3Se4 nanoparticles can exhibit giant coercivity exceeding 40 kOe at low temperature (10 K). This unusually large coercivity is attributed to the uniaxial magnetocrystalline anisotropy of the monoclinic structure of Fe3Se4 with ordered cation vacancies. The measured anisotropy constant is 1.0 × 107 erg/cm3, consistent with the result from first-principles calculations. The magnetization reversal mechanism of the nanoparticles is found to be incoherent spin rotation. [ABSTRACT FROM AUTHOR]

Ordered FePt nanodot arrays with extremely high density have been developed by physical vapor deposition using porous alumina templates as evaporation masks. Nanodot diameter of 18 nm and periodicity of 25 nm have been achieved, resulting in an areal density exceeding 1×1012 dots/in.2. Rapid thermal annealing converts the disordered fcc to L10 phase, resulting in (001)-oriented FePt nanodot arrays with perpendicular anisotropy and large coercivity, without the need of epitaxy. High anisotropy and coercivity, perpendicular easy axis orientation and extremely high density are desirable features for future magnetic data storage media applications. [ABSTRACT FROM AUTHOR]