Lightweight macroporous Co-Pt electrodeposited films with semi-hard-magnetic properties. (January 2022)

• Record Type: Journal Article
• Authors: Navarro-Senent, Cristina; Eiler, Konrad; Pané, Salvador; Sort, Jordi; Pellicer, Eva
• Is Part Of: Materials & design. Volume 213(2022)
• Publication Date: 2022-01
• Subjects: Porous films -- Co-Pt alloys -- Electrodeposition -- Magnetic properties; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2021.110369
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: Equiatomic macroporous Co-Pt films obtained by electrodeposition on titanium surfaces patterned with latex spheres of 215 nm in diameter. Annealing at 600 °C for 80 min results in coercivity enhancement from 148 to 1328 Oe while avoiding pore collapse. Increase in coercivity due to partial transformation of the initial disordered face-centered cubic phase to ordered face-centered tetragonal phase. Dense Co-Pt counterparts exhibit higher coercivity of 6.2 kOe upon annealing due to complete phase conversion. Abstract: Macroporous, partially L 10 -ordered Co-Pt films with nearly equiatomic composition were successfully synthesized by electrodeposition from an aqueous sulfate–chloride electrolyte on colloidal crystal-templated substrates, followed by annealing in vacuum. The colloids deposited on the substrate consisted of amidine-functionalized polystyrene spheres of 215 ± 13 nm in diameter, which were self-assembled by electrophoresis. As-deposited Co-Pt films obtained after the removal of the spheres showed a highly-packed arrangement of macropores. Structurally, the films showed the A1-disordered face-centered cubic (fcc) Co-Pt solid solution, accompanied by small amounts of fcc/hexagonal close-packed (hcp)–Co. Upon annealing at 600 °C, the A1-disordered phase partly transformed into the L 10 -ordered (face-centered tetragonal, fct) phase. As a result, the coercivity significantly increased from 148 Oe to 1328 Oe. Importantly, the porosity of the films was preserved after annealing. Optimum annealing temperature and time were selected on the basis of a prior parametric study with electroplated dense counterparts. This work demonstrates that the combination of colloidal crystal templating and electrodeposition is a very convenient pathway towards lightweight semi-hard magnets with potential technological applications in automotive and aerospace industries, portable sensors or spectrometers, magnetic levitation systems, or magnetoelectric devices, among others.