Magnetism of Co nanocluster films

Abstract

A cluster-beam technique is used to produce nearly monodispersed nanoclusters of Co while independently varying their size and concentration. The Co clusters are embedded in Cu and SiO 2 to form films with cluster size varying from 300 to 9000 atoms and Co concentration varying from 10 to 50 vol %. The Co magnetization (M s ) increases with increasing cluster size and decreases with increasing Co concentration for a given cluster size but is always less than the bulk value. First-principles calculations are used to analyze the experimental data in terms of the local environment effects at the cluster-matrix interface and spin-glass-like behavior due to the strong ferro-and antiferromagnetic intercluster exchange interactions for small separations.

Size dependence of nanostructures: Impact of bond order deficiency

“…Since the observation of Cox in 1985 [638], numerous experiments have been conducted on various ferromagnetic nanosolids. Repeating the same SterneGerlach deflections of Fe clusters in a molecular beam, Heer et al [629] found instead that the average magnetic moments for small iron clusters (50e230 atoms) drops with the number of atoms when the molecular beam nozzle temperatures are around 300 K. This trend is similar to those observed at room temperature of Co [632] [23] and Ni 3 Fe [637] alloy particles. Similarly, a remarkable reduction of magnetization for FeeNi invar alloy (<40 nm) [649] and Ni thin films has been observed at room temperature [627,650].…”

Influence of the Cobalt Particle Size in the CO Hydrogenation Reaction Studied by In Situ X-Ray Absorption Spectroscopy

“…Cobalt nanoparticles (NP) have found applications in data storage devices and sensors, thanks to their magnetic properties [1,2]. Cobalt is also a well known catalyst for many reactions, including growth of carbon nanotubes [3], oxidation of carbon monoxide [4], selective reduction of nitrogen oxides [5] and Fischer-Tropsch (FT) synthesis [6,7].…”

Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: Tight-binding and first-principles studies

“…The magnetic anisotropy energy of magnetic nanocrystals (e.g., Fe, Co, Ni, etc.) is the subject of intense experimental [2][3][4][5] and theoretical [6][7][8][9][10][11] studies but the ability to grow well-defined magnetic crystalline nanostructures is also a major issue [12][13][14][15][16][17][18]. This is especially the case for Fe and Co nanoclusters that can adopt various crystalline bulk structures, in particular the body-centered-cubic (bcc) and the face-centered-cubic (fcc) structures in low dimensions [15,16].…”