Magnetic relaxation studies in organic-inorganic nanoclusters

Abstract

Inorganic/organic nanocomposites of iron oxide and polypyrrole, prepared by two different techniques, namely, simultaneous gelation/polymerization and polymerization over core iron oxide particles, were investigated for their structural and magnetic properties. The presence of the polymer was confirmed by Fourier transform infrared spectroscopy. The magnetic properties were found to be very sensitive not only to the concentration of polymer but also to the method of preparation. ac susceptibility measurements performed in the temperature range of 77-300 K show the signature of superparamagnetic behavior in both the systems. The blocking temperature was found to be dependent on the cluster size and interaction effects. The frequency variation of the blocking temperature in the samples prepared by simultaneous gelation and polymerization seems to indicate weakly interacting magnetic clusters, whereas in the samples prepared by polymerization around the core oxide particles, a strongly interacting signature is seen. ac susceptibility as calculated by kinetic Monte Carlo simulations based on an interacting model for single domain particles shows a qualitative agreement with the trends observed in the experimental results.

Comparison between experimental and predicted specific absorption rate of functionalized iron oxide nanoparticle suspensions

“…In addition, several other studies have reported on the effect of aggregation on AC susceptibility of magnetic nanoparticle suspensions [28,40,41], although most look at shifts in the peak of frequency response or changes in blocking temperature. However, theoretical predictions do show that imaginary part of susceptibility is enhanced in systems with strongly interacting particles, as would be those packed in a cluster [42].…”

Mössbauer and magnetic studies in nickel ferrite nanoparticles: Effect of size distribution

“…The signatures of superparamagnetic behavior can be observed using hysteresis, where it is marked by zero coercivity and remanence and zero field cooledfield cooled (ZFC-FC) measurements where the superparamagnetic state is marked by a hump in the ZFC curve. Relaxation effects are usually studied using ac susceptibility and Mössbauer techniques [1]. Typically ac susceptibility measurements are performed in the time window of 10 À 2 -10 À 4 s and the time window for Mössbauer spectroscopy is 10 À 9 s. A systematic investigation of the blocking temperature as a function of the ac frequency helps in understanding the relaxation process and the role of interactions in the system [2].…”

Impact of interfacial interactions on optical and ammonia sensing in zinc oxide/polyaniline structures

“…Hybrid structures can be obtained by in situ polymerization of the monomer in the presence of an oxide, or by a simultaneous gelation polymerization process or formation of interfaces in the form of films (Sharma et al 2006). The sensing behaviour depends not only on the individual organic/inorganic components, but also on the nature of interface between organic and inorganic components.…”