How shape and interface determine the magnetic anisotropy of nanoparticles

Simón Oyarzún, Alexandre Tamion, Florent Tournus, Véronique Dupuis (Magnetic Nanostructures group) and Matthias Hillenkamp  (Clusters and Nanoparticles group) have published an article entitled "Size effects in the magnetic anisotropy of embedded cobalt nanoparticles: from shape to surface" in the journal Scientific Reports.

The magnetic anisotropy energy of a nano-magnet is the energy needed to reverse its magnetization, for example in a hard disk drive where the information is stored through the magnetization’s orientation of each bit. This magnetic anisotropy depends on several parameters such as the crystalline structure, the shape of the object and also its interface with the surroundings. Strong size-dependent variations of the magnetic anisotropy of embedded cobalt clusters have been evidenced quantitatively by combining magnetic measurements and advanced data treatment. The obtained values are discussed in the frame of two theoretical models that demonstrate the decisive role of the shape in larger nanoparticles and the predominant role of the surface anisotropy in clusters below 3 nm diameter.


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