Istituto dei materiali per l'elettronica ed il magnetismo     
Casoli F., Nasi L., Albertini F., Fabbrici S., Bocchi C., Germini F., Luches P., Rota A., Valeri S. Morphology evolution and magnetic properties improvement in FePt epitaxial films by in situ annealing after growth. In: Journal of Applied Physics, vol. 103 article n. 043912. American Institute of Physics, 2008.
This paper presents a detailed study of structure, morphology, and magnetic properties in FePt thin films epitaxially grown on MgO(100) at intermediate temperatures (380 C). It focuses on the effects obtained by in situ annealing the FePt films after deposition. We have demonstrated that the annealing allows one to complete the ordering, thus obtaining an epitaxial L10-FePt film with large perpendicular anisotropy (up to 3107 erg/cm3) and high perpendicular squareness and remanence ratio (both higher than 0.85). At the same time, we have found a peculiar morphology evolution by increasing the annealing time: the interconnected mazelike grains evolve towards interconnected dotlike grains of reduced size (down to 10 nm). Due to the interconnection at the grains basis, the increase in the film perpendicular coercivity with the annealing process is moderate (up to 4.1 kOe), leading to an increasing anisotropy/coercivity ratio with the annealing time. As a further step towards the understanding of the properties evolution with annealing, we have investigated the magnetic domain pattern and analyzed the domain-period dependence on the anisotropy constant in comparison with the behavior expected by the Kooy-Enz theory [C. Kooy and U. Enz, Philips Res. Rep. 15, 7 (1960)]. The main magnetic properties and reduced grain size obtained after the in situ annealing are promising to realize perpendicular recording media with reduced bit size, high thermal stability, and suitable switching field.
URL: http://link.aip.org/link/?JAPIAU/103/043912/1
DOI: 10.1063/1.2885339
Subject annealing, coercive force, grain size, iron alloys,
magnetic domains, magnetic epitaxial layers, metallic epitaxial layers, perpendicular magnetic anisotropy, platinum alloys, thermal stability
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure (for magnetic bubbles, see 75.70.Kw)
81.40.Gh Other heat and thermomechanical treatments
68.55.-a Thin film structure and morphology
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.60.Dv Thermal stability; thermal effects
75.70.Ak Magnetic properties of monolayers and thin films

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