Nano‐Sized Cobalt Cluster Films: Structure and Functionality

Abstract

An exchange interaction between magnetic clusters at ambient temperature leads to a correlated super‐spin glass state as a result of frustration between inter‐particle exchange interaction and randomly oriented intra‐particle anisotropy. In addition, after cluster oxidation a core‐shell system appears that causes an exchange bias field at cryogenic temperatures due to ferromagnetic‐antiferromagnetic coupling, which is also stabilized by cluster interactions.

Opportunities from the nanoworld: Gas phase nanoparticles

“…The Fe oxide shell was about 2 nm thick, while for Co it was 1 nm thick. CoO is formed and it leads to exchange bias effects [12,13] due to its antiferromagnetic nature. As Fig.…”

“…Metal nanoparticles were produced with a nanoparticle deposition source (http://www.oaresearch.co.uk/nanoparticle.htm) [7] where supersaturated metal vapor is generated by sputtering a metal target in an inert gas atmosphere (at pressures of ∼0.3 to 0.7 mbar) [8][9][10][11][12][13][14]. The sample chamber evacuated to 10 −8 mbar prior to the experiment.…”

“…Furthermore, for magnetic nanoparticles [3,4,[11][12][13][14][15][16][17][18][19][20][21][22] magnetic anisotropy generates magnetic easy axes with an energy barrier separating different orientations of the magnetic moment. Without an external field the magnetic moment is in a blocked state, unless thermal activation is able to overcome the anisotropy energy barrier and induce moment flipping in between easy directions (super-paramagnetism).…”

“…The ability to control surface feature on this length scale is essential in future nanotechnology. Deposition of nanoparticles has emerged as an important technique to assemble nanostructures [7][8][9][10][11][12][13][14]. The main challenges are to produce size-selected nanoparticles, and to control the interaction with the substrate so that the original nanoparticle properties are being preserved.…”

“…Small nanoparticles have a tendency to form larger nanoparticles in a process called sintering. Furthermore, in order to explore the mechanisms of structural evolution (and establish a microstructure-property relationship) in situ observations of particle crystal habit, structure, sintering and oxidation are highly indispensable [8][9][10][11][12][13][14].…”