Structural and magnetic properties of FexCu1-x sputtered thin films electrochemically treated to create nanoporosity for high-surface-area magnetic components

Abstract

Sputter deposition is a facile and widely used technique for fabricating thin-film materials. Electrochemical dealloying, on the other hand, is a promising method for creating nanoporosity, and therefore increasing surface area, in metallic materials. Surprisingly, little work has been done on the application of electrochemical dealloying to sputter-deposited thin films. Here, we prepare FexCu1-x thin films by sputter deposition to be then electrochemically treated to create porosity. We investigate the structural and magnetic properties of as-sputtered and electrochemically treated films. We find that the morphology, crystal structure, and magnetic properties are highly dependent on initial film composition. For high copper content films (Fe29Cu71), relative Cu content is found to decrease during the dealloying process. For these films, the crystal structure is not greatly affected by the induced porosity and the porous films show increased saturation magnetization. However, for the more Fe-rich compositions (Fe63Cu37), we find that Fe is preferentially lost and making the films nanoporous induces a crystal structure change from body-centered cubic (bcc) to a mixture of face-centered cubic (fcc) and bccphases. These same porous films show a decrease in saturation magnetization and a large increase in coercivity compared to the as-sputtered films. These films are attractive as high-surface-area magnetic components because of the tunability of their magnetic properties and their high surface area due to porosity. To the best of our knowledge, these results constitute the first example of nanoporous, magnetic thin films by prepared by sputtering and subsequent electrochemical treatment.