Aug 13, 2014
Tuning the magnetic properties of bimagnetic core/shell nanoparticles
Designing multi-phase transition metal oxide nanoparticles could be promising in the development of new rare-earth-free permanent magnets and high-density data-storage devices. Reporting in Nanotechnology, researchers at the Bariloche Atomic Centre in Argentina design and fabricate antiferromagnetic CoO nanoparticles encapsulated in a ferrimagnetic CoFe2O4 shell. They show that the magnetic hardness and the magnetic thermal stability can be successfully increased by the exchange coupling at the interface. Moreover, the magnetic properties can be tuned by changing the characteristic sizes of the core/shell structure.
Novel permanent magnets and high-density data-storage applications require highly anisotropic materials. Here, researchers show that the effective magnetic anisotropy can be enhanced by the exchange coupling at the interface of bimagnetic nanostructures. When the mean size of CoO/CoFe2O4 nanoparticles is reduced from 11 to 5 nm, a remarkable increase of the low-temperature coercive field from 21.5 to 30.8 kOe is observed. This is at the expense of a lower blocking temperature.
DC magnetic measurements as well as X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) experiments are carried out in order to study the relationship between the structure and the magnetic properties. A phenomenological model is used to interpret the interplay of the different competing factors on the magnetic hardening. This comprehension is essential for designing and engineering new materials to improve the performance of modern magnetic devices.
The researchers presented their work in the journal Nanotechnology 25 355704.
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About the author
Gabriel Lavorato is a PhD candidate at the Balseiro Institute in the Magnetic Resonance Laboratory of the Bariloche Atomic Centre in Argentina, supervised by Elin Winkler and Roberto Zysler. His research is devoted to the synthesis and study of bimagnetic nanoparticles within a group whose main activities cover basic research and the development of new magnetic materials with potential applications by means of different experimental techniques. This work was conducted in close collaboration with Enio Lima Jr, Dina Tobia and Horacio Troiani from the Bariloche Atomic Centre in Argentina and Dino Fiorani from the Institute of Structure of Matter of the Italian National Research Council in Italy.