Nanostructured FePt:B2O3 thin films with perpendicular magnetic anisotropy

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Abstract
FePt/B 2 O 3 multilayers were deposited by magnetron sputtering onto 7059 glass substrates. By annealing the as-deposited films at 550 °C, nanostructured FePt:B 2 O 3 films consisting of FePt grains with L1 0 structure, embedded in a glassy B 2 O 3 matrix, were obtained. The c axes of the FePt grains can be made to align with the film normal direction, which results in a perpendicular anisotropy constant of 3.5×10 7 erg/cc. The films remain layered structures after annealing when the B 2 O 3 layer thickness exceeds 16 Å. The nanostructure of the films was investigated by transmission electron microscopy. The coercivities and the average grain sizes of the films are dependent on the B 2 O 3 concentrations, with coercivities varying from 4 to 12 kOe, while average grain sizes vary from 4 to 17 nm. Strong perpendicular anisotropy, adjustable coercivity, and fine grain size suggest this nanocomposite system might have significant potential as recording media at extremely high areal density.