Nonmonotonic concentration dependence of magnetic response in Fe nanoparticle-polymer composites

Ceylan A. , Baker C., Hasanain S., Shah S.

PHYSICAL REVIEW B, cilt.72, sa.13, 2005 (SCI İndekslerine Giren Dergi) identifier identifier


We report the magnetic response of composites formed by dispersing Fe nanoparticles in a polymer. Transmission electron microscopy reveals the formation of chain-like entities of nanoparticles. The magnetic response (hysteresis, remanence ratio, exchange bias, etc.) is in general nonmonotonic as a function of the particle concentration in the composites. The coercivity and remanence go through a maximum, while the exchange bias and magnetic relaxation rates go through a minimum, with increasing concentration. The effects are interpreted as being a consequence of a competition between an increasing anisotropy due to the formation of the chain-like entities that tends to increase the remanence, etc., and the weakening of these effects at higher concentrations due to the interactions between these entities.