Experimental studies of strong dipolar interparticle interaction in monodisperse Fe3O4 nanoparticles

Abstract

Interparticle interaction of monodisperse Fe 3 O 4 nanoparticles has been experimentally investigated by dispersing the nanoparticles in solvents. With increasing the interparticle distances to larger than 100 nm in a controlled manner, the authors found that the blocking temperature ͑T B ͒ of the nanoparticles drops continuously and eventually gets saturated with a total drop in T B of 7-17 K observed for 3, 5, and 7 nm samples, compared with their respective nanopowder samples. By carefully studying the dependence of T B on the interparticle distance, the authors could demonstrate that the experimental dependence of T B follows the theoretical curve of the dipole-dipole interaction. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2778758͔The past few years have seen the field of nanoparticles virtually explode and nowadays they find possible applications in very diverse areas such as high-density magnetic storage devices and biomedicine, to name only a few. 1,2 In particular, that one can produce nanoparticles with a very narrow size distribution, or the so-called monodisperse, and in high reproducibility 3-6 rendered it possible to focus on their more intrinsic properties and associated applications. 7,8 In most prospective applications, nanoparticles are used as in solutions or nanopowders. Therefore, deeper understanding of the magnetic properties of individual nanoparticles in solution and their mutual interactions will be invaluable for numerous potential applications as well as for fundamental scientific interests.In the early 1990s, interparticle interaction was studied as origin of rather unusual glassy behavior found in nanoparticles. 9 Nanoparticles diluted using paraffin were also recently shown to have blocking temperature enhanced with increasing concentration of nanoparticles, which is attributed to their strong dipolar interaction. 10 In spite of this seemingly immediate importance of the interparticle interaction, however, there has been less systematic experimental studies on the nature of the interparticle interaction. In this letter, we present extensive studies of the magnetic properties of monodisperse Fe 3 O 4 nanoparticles dispersed in different solvents, and convincingly show that the primary interaction between nanoparticles is, as expected, the dipole-dipole interaction.For our studies, we have prepared uniform and highly crystalline nanoparticles of Fe 3 O 4 by reverse micelles method, employing microemulsions as nanoreactors and hydrated iron salts as reactants. 11 As shown in Fig. 1, transmission electron microscopy ͑TEM͒ images of the 3, 5, and 7 nm particles attest that our nanoparticles are uniform in shape and in size: 3 ± 0.34, 5 ± 0.37, and 7 ± 0.37 nm. Another noteworthy point is that our high resolution TEM ͑HRTEM͒ images shown in the insets demonstrate the good crystalline nature of the particles. Therefore, we shall ignore any possible effects related to the size distribution of the nanoparticles in the following discussion of our results. We note that once we washe...

Binary Superlattices from {Mo132} Polyoxometalates and Maghemite Nanocrystals: Long-Range Ordering and Fine-Tuning of Dipole Interactions

“…Moreover, similar effects were observed for binary assemblies prepared from colloids dispersed in toluene (Figure S4, Supporting Information). We also point out that according to the variation of T B vs. D c–c reported in the literature for interacting iron oxide nanoparticles, a ∆ T B ≈2 K should correspond to ∆ D c–c ≈1 nm, which is in good agreement with our results. As a reference, we join the FC/ZFC measurements obtained for noninteracting γ‐Fe 2 O 3 nanocrystals diluted in chloroform (Figure S5, Supporting Information, T B ≈13.7 K).…”

Magnetoresistance of Cu–Mn–Al melt-spun ribbons containing the system of interacting ferromagnetic inclusions

“…According to Ref. interaction in the real system [19]. The maxima on the ZFC and FC magnetization curves for Ribbon 1 (Fig.…”

Paramagnetic to ferromagnetic phase transition of Co doped Gd2O3 prepared by chemical route

“…The RKKY interaction is based on free electrons, but Gd 2 O 3 cannot transform into a metal at such a low doping. Dipoleedipole interaction among magnetic nanoparticles is one of the main causes for observed ferromagnetism in paramagnetic dominant weak ferromagnetic systems particularly at low temperature [23,35]. Dipole energy causes the moments at the surface of a magnetic material to get oriented along preferred directions.…”