Role of Dipolar Interactions on the Determination of the Effective Magnetic Anisotropy in Iron Oxide Nanoparticles

• DOI: 10.1002/advs.202203397
• Publication Date: 2022-12-13T02:56:52Z
• Authors: Pelayo García‐Ace...; Manuel A. Gonzále...; Ángela Arnosa‐Prieto; Lisandra de Castr...; Yolanda Piñeiro; José Rivas
• Keywords: Maghemite; Magnetic hyperthermia; Anisotropy energy; Iron oxide nanoparticles; Geomagnetic reversal

Challenging magnetic hyperthermia (MH) applications of immobilized nanoparticles require detailed knowledge the effective anisotropy constant (Keff ) to maximize heat release. Designing optimal MH experiments entails precise determination properties, which are, however, affected by unavoidable concurrence interactions in common experimental conditions. In this work, a mean-field energy barrier model (ΔE), accounting for (EA and dipolar (ED energy, is proposed used combination with AC measurements specifically developed system spherical well-controlled silica shells, acting as spacer between cores. This approach makes it possible experimentally demonstrate mean field interaction prediction interparticle distance, dij , ED ≈ 1/dij3 obtain EA asymptotic limit very large . doing so, Keff uncoupled from contributions obtained (iron oxide cores average sizes 8.1, 10.2, 15.3 nm) revealing be 48, 23, 11 kJ m-3 respectively, close bulk magnetite/maghemite values independent specific spacing shell thicknesses selected study.