Magnetic versus structural properties of Co nanocluster thin films: A magnetic force microscopy study

Abstract

Magnetic force microscopy ͑MFM͒ has been employed to study thin films consisting of low-energy-deposited cobalt nanoclusters. On continuous cluster layers a clear magnetic stray field pattern can be observed, although measurements on individual clusters are complicated by interference from topography. The magnetic correlation length determined from MFM images is substantially larger than the size of a single cluster. This indicates that the clusters are magnetically coupled to form stable domains associated with the formation of a correlated super-spin-glass state.

Opportunities from the nanoworld: Gas phase nanoparticles

“…Finally, magnetic stray fields were imaged using magnetic force microscopy (MFM). Briefly we note that magnetic tips had a coating of CoCr with thickness 50 nm and the phase maps were obtained at a lift height from the surface of 40 nm in order to eliminate direct topography effects [8,11,13]. …”

“…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].…”