  The likelihood of magnetic nanoparticles to agglomerate is usually estimated
through the ratio between magnetic dipole-dipole and thermal energies, thus
neglecting the fact that, depending on the magnitude of the magnetic anisotropy
constant ($K$), the particle moment may fluctuate internally and thus undermine
the agglomeration process. Based on the comparison between the involved
timescales, we study in this work how the threshold size for magnetic
agglomeration ($d_{aggl}$) varies depending on the $K$ value. Our results
suggest that small variations in $K$ -due to e.g. shape contribution-, might
shift $d_{aggl}$ by a few nm. A comparison with the usual
\textit{superparamagnetism} estimation is provided, as well as with the energy
competition approach. In addition, based on the key role of the anisotropy in
the hyperthermia performance, we also analyse the associated heating
capability, as non-agglomerated particles would be of high interest for the
application.

Materials Science