The correlation between superparamagnetic blocking temperatures and peak temperatures obtained from ac magnetization measurements

We study the correlation between the superparamagnetic blocking temperature T B and the peak positions T p observed in ac magnetization measurements for nanoparticles of different classes of magnetic materials. In general, T p = α+β T B . The parameters α and β are different for the in-phase (χ′) and out-of-phase (χ′′) components and depend on the width σ V of the log-normal volume distribution and the class of magnetic material (ferromagnetic/antiferromagnetic). Consequently, knowledge of both α and β is required if the anisotropy energy barrier KV and the attempt time τ 0 are to be reliably obtained from an analysis based solely on the peak positions.