Single-Crystalline Body Centered FeCo Nano-Octopods: From One-Pot Chemical Growth to a Complex 3D Magnetic Configuration

Single crystalline magnetic FeCo nanostars were prepared using an organometallic approach under mild conditions. The fine-tuning of the experimental conditions allowed the direct synthesis of these nano-octopods with body-centered cubic (bcc) structure through a one-pot reaction, contrarily to the seed-mediated growth classically used. The FeCo nanostars consist of 8 tetrahedrons exposing {311} facets, as revealed by high resolution transmission electron microscopy (HRTEM) imaging and electron tomography (ET), and exhibit a high magnetization comparable with the bulk one (M-s = 235 A.m(2).kg(-1)). Complex 3D spin configurations resulting from the competition between dipolar and exchange interactions are revealed by electron holography. This spin structures are stabilized by the high aspect ratio tetrahedral branches of the nanostars, as confirmed by micromagnetic simulations. This illustrates how magnetic properties can be significantly tuned by nanoscale shape control.

Automated summary

Single crystalline magnetic FeCo nanostars with a unique octahedral structure exposing {311} facets were prepared using an organometallic method under mild conditions, exhibiting high magnetization comparable to bulk materials. The study revealed complex 3D spin configurations resulting from the competition between dipolar and exchange interactions, which are stabilized by the high aspect ratio tetrahedral branches of the nanostars. The research demonstrates significant tuning of magnetic properties through nanoscale shape control.