The influence of particle size and interactions on the magnetization and susceptibility of nanometre-size particles

Abstract

We studied the magnetic properties of frozen magnetic liquids containing amorphous Fe1-xCx particles. By varying the particle size and concentration, we could separate single particle effects from interactions. In samples containing particles with median diameters 5.0 nm and 3.8 nm and with spontaneous saturation magnetizations 7.1 kA m-1 and 9.2 kA m-1, effects of particle interactions are observed. For 3.2 nm no interactions were observed. In samples with negligible interactions the superparamagnetic blocking temperature increases with the particle size. The effective anisotropy constant increases with decreasing particle size, implying that the anisotropy is enhanced by surface effects.

Magnetism of amorphous Fe 2 O 3 nanopowders synthesized by solid‐state reactions

“…For a particular system, the blocking temperature depends on the particle size, anisotropy energies, the time scale of the measuring technique and on the degree of the interparticle interactions. Since noninteracting systems have blocking temperature strongly dependent on the volume of individual particles [4,[17][18][19][20], the constant blocking temperature is likely to be associated with inter-particle dipolar and exchange interactions yielding a collective behaviour. Several models have been suggested to explain the magnetic behaviour of interacting systems based on dipolar and exchange interactions [3,21,22].…”

Superparamagnetism and Spin Glass Dynamics of Interacting Magnetic Nanoparticle Systems

“…[65,114,120,121]. Earlier studies use samples from different batches having slightly different physical properties [63,64,[122][123][124]. Figure 15 shows the real and imaginary part of ac susceptibility versus temperature for three different particle concentrations of the FeC sample: c = 0.06, 5, and 17 vol%.…”

Microstructural and Magnetic Properties of Core-Shell Ni-Ce Nanocomposite Particles Assemblies

“…The most prominent feature is that the blocking temperature varies as the strength of applied magnetic field changes. This indicates that, such superparamagnetic behavior can be modified by the applied field and the size distribution [11 ]. SEM images also indicates a strong interparticle interaction among those particle assemblies, and as we know, superparamgnetic properties could be modified by such like dipole-dipole interaction effect [12].…”