Thermoremanence and zero-field-cooled/field-cooled magnetization study ofCox(SiO2)

Abstract

A systematic study of Co(SiO 2 ) granular films by means of transmission electron microscopy ͑TEM͒, dc and ac initial magnetic susceptibility, and thermoremanent magnetization ͑TRM͒ is presented. The experimental results are compared with simulations of zero-field-cooled ͑ZFC͒ and field-cooled ͑FC͒ magnetization and TRM curves obtained using a simple model of noninteracting nanoparticles. The simulated ZFC/FC curves, using the actual parameters obtained from the TEM images, show a different behavior than the experimental magnetic data. The effect of the dipolar interaction among particles introduces a self-averaging effect over a correlation length ⌳, which results in a larger average ''magnetic'' size of the apparent particles together with a narrower size distribution. The analysis of the ZFC/FC curves in the framework of independent ''particle clusters'' of volume ⌳ 3 , involving about 25 real particles, explains very well the observed difference between the experimental data for the median blocking temperature ͗T B ͘ and their distribution width with respect to the ones expected from the structural observations by TEM. The experimental TRM curves also differ from those obtained from the theoretical model, starting to decrease at a lower temperature than expected from the model, also indicating the strong influence of dipole-dipole interactions.

Magnetic properties of glass-ceramics obtained by crystallization of iron-rich borosilicate glasses

“…To be more specific, Cr 2 O 3 generates Cr-based spinel-like nuclei which incorporate Fe thus creating a perfect base for further growth of magnetite crystallites (see Ref. [41] and therein references). Meanwhile, P 2 O 5 , which is a glass forming oxide, has a tendency to form phosphate complexes in borosilicate glass melts, like nonbridged Na-P species which are the critical nuclei (see Ref.…”

Memory effects in a nanoparticle system: Low-field magnetization and ac susceptibility measurements

“…17,20 It is shown that the ZFC and FC curves can be numerically obtained based on the thermal relaxation using a given size distribution and the anisotropy constant. 21 Shown in Fig. 2͑b͒ are the numerically calculated ZFC and FC curves using the size distribution and the anisotropy constant extracted from the ZFC curve in Fig.…”

Collective states of interacting ferromagnetic nanoparticles

“…frozen ferrofluids [2], discontinuous metal-insulator multilayers (DMIMs) [8,13], co-sputtered metal-insulator films [14], selforganized particle arrays on surfaces [15], focused ionbeam structured thin films [16] and mechanically alloyed materials [17].…”