Magnetism of Free and Supported Metal Clusters

Abstract

Stern-Gerlach experiments on beams of metal clusters provide detailed information on their intrinsic magnetic moments but also on the relaxation processes involved when the free clusters cross a magnetic field. For transition metal clusters of a few 10 to a few 100 atoms the observable projection of the magnetic moment onto the field axis (similar to magnetization) measured from the clusters deflection, scales with magnetic field, clusters size and inverse vibrational temperature. The measurements are in quantitative agreement with a picture in which the cluster moments are subject to rapid orientational fluctuations. Intrinsic magnetic moments per atom in excess of the bulk values are obtained for transition metal clusters such as Co, Ni, and Fe, while rare earth clusters such as Gd or Tb possess a lower magnetic moment than the bulk. For the smallest clusters, the intrinsic magnetic moment usually follows an oscillatory behavior as a function of size. In the case of rare earth clusters the magnetic behavior may even change its character from one cluster size to another. Except for some “magic numbers”, for which the statistical interpretation still holds, an anomalous spreading of the deflection profile is observed. This spreading is due to a strong coupling of the magnetic moment with the cluster body. When the moment is locked to the lattice by strong crystal field anisotropics, the rotational temperature starts to play an important role in the interpretation of experimental data.KeywordsMetal ClusterMagnetization VectorRotational TemperatureVibrational TemperatureCluster BeamThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.