Agradecimentos: This research was supported by FONDECYT - Chile Grants Nos. 1140552 and 1130950, and USM DGIIP grant PI-M-17-3. The program "Proyecto Basal" CEDENNA FB0807. AC acknowledge research funds from DIUDA-22302, MK acknowledges support from FAPESP and CNPq, brazilian agencies. Authors...

Agradecimentos: This research was supported by FONDECYT - Chile Grants Nos. 1140552 and 1130950, and USM DGIIP grant PI-M-17-3. The program "Proyecto Basal" CEDENNA FB0807. AC acknowledge research funds from DIUDA-22302, MK acknowledges support from FAPESP and CNPq, brazilian agencies. Authors acknowledge to anonymous referees for their valuable discussion, suggestions and comments that have enormously enriched the present work

Abstract: We study the effect of the uniaxial anisotropy in a system of ideal, noninteracting ferromagnetic nanoparticles by means of a thermodynamical model. We show that the effect of the anisotropy can be easily assimilated in a temperature shift T*(a), in analogy to what was proposed by Allia et...

Abstract: We study the effect of the uniaxial anisotropy in a system of ideal, noninteracting ferromagnetic nanoparticles by means of a thermodynamical model. We show that the effect of the anisotropy can be easily assimilated in a temperature shift T*(a), in analogy to what was proposed by Allia et al. (2001) in the case of interacting nanomagnets. The phenomenological anisotropic T*(a) parameter can be negative, indicating an antiferromagnetic-like behavior, or positive, indicating a ferromagnetic-like character as seen in the inverse susceptibility behavior as a function of temperature. The study is done considering an easy axis distribution to take into account the anisotropy axis dispersion in real samples (texture). In the case of a volumetric uniform distribution of anisotropy axes, the net effect makes T*(a) to vanish, and the magnetic susceptibility behaves like a conventional superparamagnetic system, whereas in the others a finite value is obtained for T*(a). When magnetic moment distribution is considered, the effect is to enhance the T*(a) parameter, when the dispersion of the magnetic moments becomes wider

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ

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