Electrodeposition of Equiatomic FePt Permanent Magnets from Non-Aqueous Electrolytes Based on Ethylene Glycol

Abstract

The highly ordered L10 hard-magnetic phase of the equiatomic FePt alloy is of significant interest for a great number of applications, ranging from the realization of magnetic sensors to the deposition of thin layers for vertical recording. In this context, the development of wet deposition processes able to yield high-quality layers of FePt represents a need of considerable industrial relevance. While several aqueous-based electrodeposition approaches have been developed for the manufacturing of FePt, these formulations evidenced substantial technological limitations, specifically connected to the use of water as solvent. The present work describes the deposition of FePt from a non-aqueous electrolyte based on ethylene glycol, which presents potential advantages in terms of gas evolution reduction and purity improvement of the obtained coatings. Deposition was 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 were easily obtained. After annealing at 600 °C, their microstructure changed and the disordered fcc phase present in the as-plated alloy evolved into the highly magneto-crystalline anisotropic L10 phase. As a consequence, coercivity reached values in excess of 10 kOe.