The dominant magnetic relaxation mechanism can be controlled by changing the effective magnetic anisotropy in core/shell nanoparticles, preserving its magnetic saturation, size and morphology for hyperthermia experiments.
We report the precise control of tunneling magnetoresistance (TMR) in devices of self-assembled core/shell Fe 3 O 4 /Co 1−x Zn x Fe 2 O 4 nanoparticles (0 ≤ x ≤ 1). Adjusting the magnetic anisotropy through the content of Co 2+ in the shell, provides an accurate tool to control the switching field between the bistable states of the TMR. In this way, different combinations of soft/hard and hard/soft core/shell configurations can be envisaged for optimizing devices with the required magnetotransport response. * winkler@cab.cnea.gov.ar 1 arXiv:2005.10771v1 [cond-mat.mes-hall] 21 May 2020
Magnetic effects caused by dipolar interactions in single-domain magnetic ensembles at finite temperatures are described. A modified superparamagnetic approach based on the mean field theory and random anisotropy model has been developed to describe the magnetization curves of nanoparticle assemblies. The model was used to fit experimental zero-field-cooled and field-cooled magnetization curves in Fe 3 O 4 nanoparticles embedded in paraffin. The fitting parameters were based on structural properties of the materials and the strength of the interactions between nanoparticles. The model provides a quantitative description of the effects of the nanoparticle interaction with good agreement with the experiment. In addition, the model was adapted to describe magnetic properties of a NiFe thin film patterned into a nanodot array, showing potential to be used as a framework to predict magnetic interaction effects in high-density 2D arrays such as bit patterned media.
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