We study the magnetocaloric effect (MCE) in parallel one-dimensional chains of dipole-dipole interacting magnetic nanoparticles with collinear magnetic anisotropy axes. By means of a Monte Carlo method we simulate the magnetic field dependence of the MCE for a field applied perpendicular to the anisotropy axes, finding the coexistence of direct and inverse MCE being both of reversible character. The inverse MCE-temperature range is quite small and progressively shifts to lower temperatures with increasing applied field until it disappears, thus we have mainly focused our study on the direct MCE-temperature range. We show the existence of a particular magnetic field value being proportional to the anisotropy field of the particles, $H^{\ast }\approx 2.5H_{\text{A}}$, which optimizes the magnetic entropy change and refrigerant capacity of the collinear aligned ensemble of nanoparticles.

• Received 9 September 2009

DOI:https://doi.org/10.1103/PhysRevB.80.134421