Magnetic dynamics of Zn/sup 57/Fe/sub 2/O/sub 4/ nanoparticles dispersed in a ZnO matrix

Abstract

The magnetic properties of diluted ZnFe 2 O 4 nanoparticles with nearly normal spinel structure, dispersed in a nonmagnetic ZnO matrix, are presented. A magnetic transition to an ordered state is observed at about 19 K, from Mössbauer and magnetic measurements. Detailed characterization of the frequency and field dependence shows that, below the magnetic transition, the system displays several features that suggest a collective freezing of ferrimagnetic particles. Although single-domain particles are inferred from structural data, a dynamic study of this transition hints toward a spin-glass-like process, with = 17 0(4) K and critical parameters = 20 2, much higher than those of canonical spin glasses. Some facets of these large critical parameters in fine-particle systems are discussed.

Synthesis and characterization of ZnFe2O4 magnetic nanoparticles via a PEG-assisted route

“…However, since there is antiferromagnetic interactions both in intra-clusters and interclusters spins, and size (effective moment) distribution of the particles, the resultant overall magnetic behavior would naturally be expected to be considerably different than that of conventional super-paramagnetic systems. This results supports predictions of Oliver and Chinnasamy et al for spin-glass-like behavior for nanosized ZnFe 2 O 4 particles [42][43][44].…”

“…It is found that ZFC and FC curves overlap and a peak of magnetization about 19 emu/g at the temperature of 16 K was observed. While in the case of M-T curve with 20 Oe applied field, the peak increases to about 23 K, which is due to the decrease of the interactions among the particles with decreasing applied magnetic field as observed in other studies [46,47].…”

“…Partial migration of Fe atoms from A to B sites yields ferrimagnetic clusters due to the strong A-B superexchange interactions. This type of cationic inversion has been invoked as the source of the much larger T N observed in Zn-ferrite nanoparticles as in our case [46].…”

“…The increase in inversion parameter causes the increase in magnetization as in our case [42][43][44]. Since our sample has a 14 nm particle size, the inversion parameter may be larger.…”

Synthesis of protoporphyrin coated superparamagnetic iron oxide nanoparticles via dopamine anchor

“…In nanoparticles especially below 10 nm the magnetic anisotropy constant increases drastically while decreasing sizes. Large values of K in nanoparticles may be attributed to dipolar interactions for concentrated systems and surface effects mainly in diluted systems [34,35] (Fig. 5).…”