Abstract
Cu1−xFexO nanoparticles were prepared using a freeze-drying process followed by heat treatment. The particles were then characterized using Mössbauer spectroscopy and magnetization techniques. The results revealed complex magnetic behavior, which can be attributed to the presence of two different magnetic regions: the particle core, which has antiferromagnetic fluctuations, and the particle shell, where uncompensated spins are responsible for their superparamagnetic characteristics. At low temperatures, the moments freeze, revealing a ferromagnetic order for the shells and a dipolar magnetic interaction among the nanoparticles. In addition, an exchange-bias field revealed magnetic interactions between the core and the shell of the nanoparticles. The ferromagnetism observed in this system suggests that antiferromagnetic oxide matrices can be used for diluted magnetic semiconductor applications, if suitably doped.
Highlights
Materials that could transport a spin-polarized electric current have attracted much attention in recent decades
The results revealed complex magnetic behavior, which can be attributed to the presence of two different magnetic regions: the particle core, which has antiferromagnetic fluctuations, and the particle shell, where uncompensated spins are responsible for their superparamagnetic characteristics
The ferromagnetism observed in this system suggests that antiferromagnetic oxide matrices can be used for diluted magnetic semiconductor applications, if suitably doped
Summary
Materials that could transport a spin-polarized electric current have attracted much attention in recent decades. The interest has been triggered by theoretical models that predicted that a nonmagnetic oxide matrix doped with magnetic cations should present a ferromagnetic (FM) order at room temperature (RT).. The interest has been triggered by theoretical models that predicted that a nonmagnetic oxide matrix doped with magnetic cations should present a ferromagnetic (FM) order at room temperature (RT).1,2 Such materials are called diluted magnetic oxides (DMOs), which have been prepared through several combinations of hosts (e.g., III-V semiconductors) and magnetic cations (e.g., Mn, Co, and Fe).. The absence of conclusive results is partly due to the possible formation of minor (magnetic) phases during DMO synthesis These spurious phases are difficult to identify and could mask the true (non-)magnetic nature of the prepared solid solutions. Some promising DMO candidates are only FM at low temperatures, making them unsuitable for RT applications and demanding further investigation
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