Soft-hard magnetic phase tuning of FeCo nanowire arrays by electrodeposition current density.

Abstract

A better understanding of magnetic phases and interactions in nanomaterials can provide new pathways for the development of tunable magnetic storage media, facilitating their design and integration in nanodevices. Here, we use a pulse electrochemical method, and change the electrodeposition current density (J_ed) in the range of 12.50-37.50 mA cm^-2in order to fabricate FeCo nanowire arrays (NWAs) in mild-anodized aluminum oxide membranes. While the length and composition of the NWs are not considerably affected with increasingJ_ed, we observe obvious changes in the shape of magnetic hysteresis curves, arising from the coupling of soft-hard phases. By investigating the crystalline properties of the NWAs, the hard phase is attributed to almost Fe₅₀Co₅₀alloy structure, whereas the soft phase is due to the presence of magnetic oxides, including CoO and FeO. We obtain first-order reversal diagrams to study the two phases in more detail, indicating the involvement of interference and complex features. The increasing trends observed in hysteresis curve coercivity and squareness from 416 to 1752 Oe and 0.12-0.80 with increasingJ_edfrom 12.50 to 37.50 mA cm^-2, respectively, are accompanied with significant reductions in soft phase intensity and interphase magnetic interactions. Our results indicate the possibility of tuning soft-hard magnetic phases in FeCo NWAs through controllingJ_edduring the electrodeposition process in the membranes.