Micromagnetic modeling of inter-particle interactions and their impact on hysteresis and energy in pseudo-single-domain iron nanoparticles

This work investigates the effects of inter-particle interactions on hysteresis and energy contributions in 42 nm iron nanoparticles within the pseudo-single-domain regime, a size where non-uniform spin textures compete with dipolar coupling. Using Ubermag/OOMMF to solve the Landau–Lifshitz–Gilbert equation, we provide a systematic decomposition of all four magnetic energy terms as a function of inter-particle separation. At short separations, strong dipolar interactions induce collective behavior characterized by enhanced coercivity ( ∼ 70 mT) and remanence ( ∼ 0.38 M s ), and the emergence of non-collinear spin textures and vortex-like configurations. These states lead to elevated exchange and demagnetizing energy contributions. As separation increases, dipolar coupling weakens, leading to a transition toward independent-particle behavior, characterized by reduced coercivity and remanence, but higher saturation fields. This study provides novel quantitative insights into interaction-driven reversal mechanisms in this critical pseudo-single-domain range, relevant for the design of dense assemblies in high-density data storage, magnetic sensing, spintronics, and biomedical applications.