Structural and magnetic properties of high-energy ball-milled nanoparticles CoFe₂O₄ via neutron diffraction study

Abstract

In this study, we investigated the structural and magnetic properties of high-energy ball-milled CoFe₂O₄ nanoparticles using neutron powder diffraction. Rietveld refinement confirmed the structural stability of the single-phase cubic spinel (Fd-3m) during milling up to 120 min. However, the lattice parameters, including the lattice constant, bond lengths, and bond angles change with milling time. In particular, milling leads to a widening of the B–O–B bond angles and a narrowing of the A–O–B bond angles, which enhances the antiferromagnetic superexchange interaction J_AB. The refinement also reveals significant changes in the magnetic moments at the tetrahedral and octahedral sites. The variation in the average magnetic moments closely follows the evolution of the inversion degree, indicating that the reduction in magnetic moments is associated with the decrease in inversion degree during the milling process. These findings contribute to a deeper understanding of structure–property relationships in nanosized CoFe₂O₄ and provide meaningful guidance for tuning its magnetic performance through mechanical processing.