W. C. Nunes

Temperature dependence of the coercive field in single-domain particle systems

The magnetic properties of

Competing interparticle interactions and surface anisotropy in NiO nanoparticles

{\mathrm{Cu}}_{97}{\mathrm{Co}}_{3}

Magnetic behavior of Ni nanoparticles with high disordered atomic structure

and

Coercivity extrema in melt-spun CuCo ribbons: Effects of the magnetic moment distribution

{\mathrm{Cu}}_{90}{\mathrm{Co}}_{10}

Atomic force microscopy and magnetization investigation of a water-based magnetic fluid

granular alloys were measured over a wide temperature range

Magnetic properties in granular Co10Cu90 alloys: the effect of random anisotropy and interparticle interactions

(2\char21{}300\phantom{\rule{0.3em}{0ex}}\mathrm{K})

Exchange bias in Fe/EuTe(111) bilayers

. The measurements show an unusual temperature dependence of the coercive field. A generalized model is proposed and explains well the experimental behavior over a wide temperature range. The coexistence of blocked and unblocked particles for a given temperature raises difficulties that are solved here by introducing a temperature dependent blocking temperature. An empirical factor gamma

Granular Cu-Co alloys as interacting suparparamagnets

(\ensuremath{\gamma})

Preparation of Magnetite Nanoparticles in Mesoporous Copolymer Template

arises from the model and is directly related to the particle interactions. The proposed generalized model describes well the experimental results and can be applied to other single-domain particle system.

Susceptibility investigation of the nanoparticle coating-layer effect on the particle interaction in biocompatible magnetic fluids

We report unconventional magnetic properties on NiO nanoparticles of an average diameter ∼5.8(7) nm obtained by coprecipitation method. To investigate the effect of the intra and interparticles interactions in the magnetic properties nanoparticles were dispersed in a polyvinyl-pyrrodone matrix at two different concentrations. X-ray, ac, and dc magnetization and ferromagnetic resonance experiments were carried out on powder and dispersed NiO systems. Our results show that dispersed and concentrated samples exhibit following two different magnetic behaviors: (i) a high temperature peak related to the blocking of the particle core and (ii) a low temperature maximum likely related to the freezing of the frustrated spins on surface particle. Besides, we have observed that the low temperature maximum is not field-dependent and depend strongly on the distance among particles. This result can be understood taking account the decreasing of the dipolar interaction to more dispersed samples.