Self-assembly FePt nanoislands: surface studies and magnetic properties

Self-assembly FePt nanoislands: surface studies and magnetic properties

Cantelli, V.; von Borany, J.; Grenzer, J.

L10 ordered, c-axis oriented FePt thin films belong to the most promising ferromagnetic materials for future magnetic storage media; but the coercive filed could be significantly improved if changing from homogeneous to granular films or even to FePt nanoislands arrays . This contribution describes the formation of self-assembled FePt nanoislands on amorphous SiO2/Si substrates by conventional DC magnetron sputtering. Ag is well known to follow the Volmer-Weber growth on SiO2: the as-deposited Ag islands are exploited as substrate for the FePt granular layer. If a characteristic ratio between Ag and FePt amonut is respected, no nano-islands agglomeration was observed after annealing at 450°C for 30 minutes. This effect is here explained in terms of thermal buget given to the system during deposition and the demand of a unimodal size distribution of the Ag nanoislands. From synchrotron x-ray GISAS investigations, the FePt islands have a pallet like shape with a 30 nm average diameter and 18 nm average height. SEM and AFM analysis didn't prove any order in the pallets placement over the SiO2. After annealing, the strong ferromagnetic L10 phase was detected by XRD. But, either SQUID or MFM measurements evidence no difference between a granular FePt layer without Ag and with Ag pallets as buffer, and an enhanced coercivity of FePt thin granular films has been confirmed, in comparison to thick homogeneous FePt layers.

Keywords: FePt; DC magnetron sputtering; Ag; nanoislands

  • Lecture (Conference)
    7th Autumn School on X-ray scattering from surfaces and thin layers, 04.-06.10.2007, Smolenice, Slovakia

Publ.-Id: 10729