  The performance of magnetic nanoparticles is intimately entwined with their
structure, mean size and magnetic anisotropy. Besides, ensembles offer a unique
way of engineering the magnetic response by modifying the strength of the
dipolar interactions between particles. Here we report on an experimental and
theoretical analysis of magnetic hyperthermia, a rapidly developing technique
in medical research and oncology. Experimentally, we demonstrate that
single-domain cubic iron oxide particles resembling bacterial magnetosomes have
superior magnetic heating efficiency compared to spherical particles of similar
sizes. Monte Carlo simulations at the atomic level corroborate the larger
anisotropy of the cubic particles in comparison with the spherical ones, thus
evidencing the beneficial role of surface anisotropy in the improved heating
power. Moreover we establish a quantitative link between the particle
assembling, the interactions and the heating properties. This knowledge opens
new perspectives for improved hyperthermia, an alternative to conventional
cancer therapies.
