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.

Further reading

Heat-assisted magnetic recording doubles hard disk drive capacity (June 2014)
Competing interactions and stepwise magnetization observed in Fe nanoparticle films (Aug 2013)
Making monodisperse FeCo nanoparticles the easy way (Oct 2013)