Regular Fe3O4 octahedrons with excellent soft magnetic properties prepared by dealloying technique

[Display omitted] •Regular Fe3O4 octahedrons was successfully fabricated by dealloying technique.•Dealloying factors were compared and optimized to obtain Fe3O4 octahedrons.•The presently prepared Fe3O4 octahedrons revealed good magnetic properties.•The Fe3O4 octahedrons exhibited a promising application prospect. The dealloying processes of Al–15Fe (at.%) alloy ribbons consisting of two distinct phases of α-Al (Fe) and Al13Fe4 in NaOH solutions were investigated. The effects of NaOH solution concentration, dealloying temperature and time on the results were comparatively discussed. The as-dealloyed samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). It was found that all of the three experimental conditions could affect the morphology of the as-dealloyed samples, and the influence of solution concentration was the crucial factor. The Al could be leached out from both the α-Al (Fe) and Al13Fe4 phases to obtain regular octahedral Fe3O4 under most of the experimental conditions except for that in the 0.5molL−1 NaOH solution at ambient temperature. In particular, the Fe3O4 from dealloying Al–15Fe ribbons in 5molL−1 NaOH solution for 48h at ambient temperature shows a uniform octahedral structure (average edge length: 667±158nm) and special magnetic properties (saturation magnetization: 83.3emug−1, residual magnetization: 10.4emug−1 and coercive force: 256.9Oe), implying its potential applications in magnetic fluid, information storage, etc.