Abstract
The effect of cobalt doping on the magnetic properties of Mn1−xCoxFe2O4 nanoparticles was investigated. All samples consist of ensembles of nanoparticles with a spherical shape and average diameter of about 10 nm, showing small structural changes due to the substitution. Besides having the same morpho-structural properties, the effect of the chemical composition, i.e., the amount of Co doping, produces marked differences on the magnetic properties, especially on the magnetic anisotropy, with evident large changes in the coercive field. Moreover, Co substitution has a profound effect on the interparticle interactions, too. A dipolar-based interaction regime is detected for all samples; in addition, the intensity of the interactions shows a possible relation with the single particle anisotropy. Finally, the sample with the strongest interaction regime shows a superspin glass state confirmed by memory effect dynamics.
Highlights
A strong scientific interest has driven the fundamental research on magnetic nanoparticles in the last decades [1,2,3,4], with interest constantly fed by their wide range of potential applications, e.g., from catalysis [5] and microwaves applications [6] to biomedicine, such as MRI [7], hyperthermia [8], and drug delivery [7,9] applications
We investigate the structural and magnetic properties of ensembles of ferrite nanoparticles with formula Mn1−xCoxFe2O4, (0 ≤ x ≤ 1) prepared by a combined lowenergy ball milling and self-combustion method
The effect of cobalt doping on the magnetic properties of Mn1−xCoxFe2O4 nanoparticles prepared by low-energy ball milling was investigated
Summary
A strong scientific interest has driven the fundamental research on magnetic nanoparticles in the last decades [1,2,3,4], with interest constantly fed by their wide range of potential applications, e.g., from catalysis [5] and microwaves applications [6] to biomedicine, such as MRI [7], hyperthermia [8], and drug delivery [7,9] applications. Because the samples are dense ensembles of particles in close proximity, special attention was devoted to the analysis of the interactions, showing the competitive effect of magnetic anisotropy and interparticle interactions. It is well known that in ensembles of magnetic nanoparticles, the FC curve diverges from the ZFC curve, and the system shows magnetic irreversibility behaviour below a given temperature (Tirr), Figure 2: As an example of the size, shape and crystalline quality of the samples, TEM images of C0 (a) and C100 (b) samples are reported.
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