(Invited) Electrodeposition of Fe-Pt Magnetic Films and Multilayers with Largemagnetic Anisotropy for Magnetic Recording and Microsystems

Alloys of Pt with metals of the Fe group form various phases with large magnetic anisotropy (above 1 MJ/m3), in particular the L10 phases of equiatomic Fe-Pt and Co-Pt. These alloys are promising candidates for permanent magnet components in magnetic MEMS or magnetic storage media.

Electrochemical growth of magnetic films presents unique advantages, such as the close control of the driving force for film growth to finely tune properties via various deposition modalities, and the ability to form micro- or nano-structures of high aspect ratio via purely additive processes. This talk will discuss the electrochemical synthesis, structural characterization and magnetic properties of equiatomic Fe-Pt alloy films, highlighting the unique features afforded by electrochemical processing. 

As-deposited equiatomic Fe-Pt alloys are obtained by an underpotential codeposition process; these films exhibit a metastable face-centered cubic structure in the as-deposited condition, but formation of the tetragonal L10 phase and coercivities of up to 14 kOe can be achieved via thermal annealing of the films at only 450C [1, 2]. The composition of Fe-Pt alloys can be easily varied during growth by potential pulsing, enabling the formation of multilayers with a compositional gradient. Thermal annealing of Fe75Pt25/Fe50Pt50 bi- and multi-layers in forming gas results in a significant acceleration of the phase transformation to the L10 phase, enabling the formation of highly coercive films at lower annealing temperature. The quality of the multilayers is inferred by the observation of exchange-coupled behavior at about 5 nm sublayer thickness.

[1] D Liang, JJ Mallett, G Zangari, ACS Appl Mater Interfaces 2 (4) 961-964 (2010);
[2] D. Liang, S. Ge, G. Zangari, IEEE Trans Magn. DOI: 10.1109/TMAG.2015.2394326 (2015)