Magnetic behavior of iron (III) oxyhydroxy nanoparticles in organic-inorganic hybrid matrices

Magnetic properties of iron(III) oxyhydroxy nanoparticles stabilized within a sol-gel derived organic-inorganic matrix are investigated. Depending on the size of the polymer chain and on the sol-gel route, ferrihydrite or Fe(III) oxyhydroxynitrate can be formed. Comparing different sets of samples we can address the observed magnetic features to the different oxyhydroxy phases. The ferrihydrite particles exhibit thermal and field irreversibility below 30 K, with coercive and exchange fields characteristic of antiferromagnetic nanoparticles uncompensated/canted spins. The existence of antiferromagnetic interactions in the Fe(III) oxyhydroxynitrate phase can be inferred.