The highly ordered L1₀ hard-magnetic phase of the equiatomic FePt alloy is of significant interest for a great number of magnetic applications, ranging from the realization of micromagnets for integrated sensors to the deposition of thin layers for vertical recording media [1]. In this context, the development of wet deposition processes able to yield high-quality layers of FePt represents a topic of considerable industrial relevance. Even though several aqueous-based electrodeposition approaches have been developed for the manufacturing of FePt, most formulations evidenced substantial technological limitations, specifically connected to the use of water as solvent (hydrogen evolution, oxygen contamination of the deposit...).

From this point of view, non-aqueous electrolytes represent a promising alternative for the electrosynthesis of metallic layers. These alternative solvents are characterized by attractive applicative properties: they present wide electrochemical windows, are simple to prepare, formulated from relatively cheap components, almost unreactive with water and, in most cases, biodegradable. Thanks to these properties, they have been widely employed for the electrodeposition of metals [2], alloys [3] or composites [4].

The present work describes the deposition of FePt from a non-aqueous electrolyte based on ethylene glycol, which presents potential advantages over water-based baths in terms of gas evolution reduction and purity improvement of the obtained coatings. Deposition is carried out using Fe(III) and Pt(IV) as precursors and ammonium chloride as additive to enhance the quality of the coatings and their compositional uniformity. In this way, equiatomic FePt thin films characterized by a good morphology are easily obtained. These layers are subsequently characterized to assess their morphology, phase composition and magnetic properties. After annealing at 600 °C, the microstructure changes and the disordered face centered cubic phase present in the as-plated alloy evolves into the highly magneto-crystalline anisotropic L1₀ phase. As a consequence, the coercivity of the layers reaches values in excess of 10 kOe.

[1] Lodder et al.; Encyclopedia of Materials: Science and Technology, pp. 1-10 (2005)

[2] Abbott et al.; Phys. Chem. Chem. Phys. 8, 4265-4279 (2006)

[3] Bernasconi et al.; J. Phys. Chem. B 124(47), 10739-10751 (2020)

[4] Rosoiu et al.; Metals 10(11), 1455 (2020)