Ingested and biomineralized magnetic material in the prey Neocapritermes opacus termite: FMR characterization

The temperature dependence of Ferromagnetic Resonance spectra, from 5K to 280K, was used to study the magnetic material present in Neocapritermes opacus termite, the only prey of the Pachycondyla marginata ant. The analysis of the resonant field and peak-to-peak linewidth allowed estimating the particle diameters and the effective anisotropy energy density, K(EFF), as a sum of the bulk and surface contributions. It allowed to magnetically distinguish the particles of termites as collected in field from those of termites after 3 days under a cellulose diet, introduced to eliminate ingested/digested material. The data also, suggest the presence of oriented magnetite nanoparticles with diameters of 11.6+/-0.3nm in termites as collected in field and (14.0+/-0.4nm) in that under a cellulose diet. Differences between their K(EFF) and its components are also observed. Two transitions are revealed in the resonant field temperature dependence, one at about 50K that was associated to surface effects and the other at about 100K attributed to the Verwey transition.