Magnetization Reversal Mechanism and Microstructure Refinement of the FePt (001) Nanogranular Films With SiO$_{2}$ Capping Layer

Abstract

Ordered FePt continuous thin films with an amorphous SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> single capping layer have been fabricated on MgO (001) single-crystal substrates by the electron beam deposition technique at 400degC in order to investigate the effects of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> capping layer on microstructure and magnetic reversal process of the FePt (001) thin films. The formation of nanogranular-like FePt films was directly obtained with this process due to the interpenetration of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> which has a lower surface energy than that of pure Fe or Pt. Studies of angular dependent coercivity show a tendency of a domain-wall motion weaken towards rotation of reverse-domain type upon thickness of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> capping layer on the FePt thin films. The intergrain interaction was confirmed from the Kelly-Henkel (delta <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> ) plot that indicated the strong exchange coupling between neighboring grains in the FePt continuous films without SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> capping layer. On the other hand, negative delta <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> value was obtained when the FePt films with SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> capping layer, indicating the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> capping layer, can lead to the reduction of intergrain exchange coupling thus presence of dipole interaction in the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /FePt nanocomposite thin film structures.