Magnetic material arrangement in oriented termites: a magnetic resonance study

Temperature dependence of the magnetic resonance is used to study the magnetic material in oriented Neocapritermes opacus (N.o.) termite. the only prey of the migratory ant Pachycondyla marginata (P.m.). A broad line in the g = 2 region, associated to isolated nanoparticles shows that at least 97% of the magnetic material is in the termite's body (abdomen + thorax). From the temperature dependence of the resonant field and from the spectral linewidths, we estimate the existence of magnetic nanoparticles 18.5 +/- 0.3 nm in diameter and an effective magnetic anisotropy constant, K-eff between 2.1 and 3.2 x 10(4) erg/cm(3). A sudden change in the double integrated spectra at about 100 K for N.o. with the long body axis oriented perpendicular to the magnetic field can be attributed to the Verwey transition, and suggests an organized film-like particle system. (C) 2004 Elsevier Inc. All rights reserved.