Novel Hybrid Ferromagnetic Fe-Co/Nanodiamond Nanostructures: Influence of Carbon on Their Structural and Magnetic Properties

This study introduces a novel magnetic nanohybrid material consisting of ferromagnetic (FM) bcc Fe-Co nanoparticles (NPs) grown on nanodiamond (ND) nanotemplates. A combination of wet chemistry, which produces chemical precursors and their subsequent thermal treatment under vacuum, was utilized for its development. The characterization and study of the prepared samples performed with a range of specialized experimental techniques reveal that thermal treatment of the as-prepared hybrid precursors under a range of annealing conditions leads to the development of Co-rich Fe-Co alloy NPs, with average sizes in the range of 6-10 nm, that exhibit uniform distribution on the surfaces of the ND nanotemplates and demonstrate FM behavior throughout a temperature range from 2 K to 400 K, with maximum magnetization values ranging between 18.9 and 21.1 emu/g and coercivities ranging between 112 and 881 Oe. Moreover, Fe-57 M & ouml;ssbauer spectroscopy reveals that apart from the predominant bcc FM Fe-Co phase, iron atoms also participate in the formation of a secondary martensitic-type Fe-Co phase. The emergence of this distinctive phase is attributed to the diffusion of carbon atoms within the Fe-Co lattices during their formation at elevated temperatures. The source of these carbon atoms is related to the unique morphological properties of the ND growth matrices, which facilitate surface sp(2) formations. Apart from their diffusion within the Fe-Co NP lattice, the carbon atoms also reconstruct layered graphitic-type nanostructures enveloping the metallic alloy NPs. These non-typical nanohybrid materials, reported here for the first time in the literature, hold significant potential for use in applications related, but not limited to, biomedicine, biopharmaceutics, catalysis, and other various contemporary technological fields.