The resonance decay function method in the determination of the pre-factor of the Néel relaxation time of single-domain nanoparticles

► Experimental technique centred on the measurement of the complex magnetic susceptibility, χ(ω,H)=χ′(ω,H)−iχ″(ω,H). ► Precessional decay time of the Landau-Lifshitz equations is evaluated. ►Néel pre-factor, τ0N, determined for single-domain magnetite particles of mean diameter 10 nm. ► After-effect function, b(t), obtained through the relationship, which exists between b(t) and χ″(ω).