Role of Dipolar Interactions and Volume Particle Size Distribution on the Nonmonotonic Magnetic Field Dependence of the Blocking Temperature in Magnetic Nanoparticles

The nonmonotonic behavior of the magnetic field dependence H of the superparamagnetic blocking temperature TB(H) (or Tmax(H)) of an assembly of magnetic nanoparticles NPs was studied both experimentally and theoretically. We have combined the measurements of zero-field cooling ZFC magnetization curves under H performed on samples with increasing concentration of Ni nanoparticles and Monte Carlo simulations. As a result, we have found that increasing the strength of the dipolar interaction between granules and the occurrence of a very narrow width of a log-normal volume particle size distribution of the NPs suppress the nonmonotonic behavior of Tmax(H).