The influence of anisotropy on the microstructure and magnetic properties of dipolar nanoplatelet suspensions

Abstract

In recent years, there has been an increasing interest in magnetic nanoparticles with non-spherical shapes. This is largely due to their broad span of tuneable properties, which allow for tailoring...

Structure and dynamics in suspensions of magnetic platelets

“…This can be seen by comparing (for instance) the light green column in the lower right corner to the yellow structure in the lower left, where most of the platelets are aligned in a column, but an additional platelet at the lower left corner of the aggregate is attached at an angle. As discussed in detail in previous work, 14 when two spheres form an energetically stable bond, their dipoles are oriented head-to-tail. This energy minimum is rather deep and wide, so that even relatively large thermal-noise induced angular fluctuations cannot break such a bond.…”

“…It should be noted, though, that the clustering is predominantly based on a distance criterion,‡‡As in ref. 14 there were additional checks on the dipole alignment and negative interaction energy to reduce false positives in weakly interacting systems. However, since clusters at high concentrations will interact, this is not sufficient to differentiate them. and hence the distinction between clusters becomes blurred at high concentrations, but p ( n ) gives some idea of how the particles are associated.…”

“…‡As in ref. 14 there were additional checks on the dipole alignment and negative interaction energy to reduce false positives in weakly interacting systems. However, since clusters at high concentrations will interact, this is not sufficient to differentiate them.…”

“…However, this result is not very surprising, because the correlations between platelets are very different from those between spheres, as detailed previously in ref. 14. Locally, the correlations between two platelets are determined by their steric anisotropy, and can be better characterised by a normalised orientational order parameter, Q ∼ tanh( κϕ ), where κ is a system specific constant.…”

“…Unless otherwise specified, the static properties presented in Section 3.1 were calculated using the same methodology as described in ref. 14. This is mostly relevant for the clustering, where an adjusted distance cutoff was used to account for the anisotropy of the platelets.…”