Magnetic properties, metal clusters

In the present work, our focus is on the properties of the magnetic transition metal clusters and, in particular, on Ni clusters for which experimental data are available for comparison. Using the procedures discussed above, we have calculated the melting, j , and the Curie, temperatures of the Nij clusters for N < 201. These results were discussed recently in Andriotis et al. (2007). The melting temperature has been derived on the basis of the Lindemann... 

Small metal clusters are also of interest because of their importance in catalysis. Despite the fact that small clusters should consist of mostly surface atoms, measurement of the photon ionization threshold for Hg clusters suggest that a transition from van der Waals to metallic properties occurs in the range of 20-70 atoms per cluster [88] and near-bulk magnetic properties are expected for Ni, Pd, and Pt clusters of only 13 atoms [89] Theoretical calculations on Sin and other semiconductors predict that the stmcture reflects the bulk lattice for 1000 atoms but the bulk electronic wave functions are not obtained [90]. Bartell and co-workers [91] study beams of molecular clusters with electron dirfraction and molecular dynamics simulations and find new phases not observed in the bulk. Bulk models appear to be valid for their clusters of several thousand atoms (see Section IX-3). 

One of tire interesting aspects of transition-metal clusters is tlieir novel magnetic properties [91, 92, 93 and 94l]. ... 

Pastor G M, Dorantes-Davila J and Bennemann K H 1989 Size and structural dependence of the magnetic properties of small 3d-transition metal clusters Phys. Rev. B 40 7642... 

The electronic, optical, and magnetic properties of metal clusters are of great current interest, but these properties have been little studied with very mixed -metal clusters. This is to some extent a reflection of the difficulty of preparing high-nuclearity examples many of these interesting properties become important upon increasing cluster size. The limited magnetic studies to date are... 

Figure 1. Schematic illustration of the laser-vaporization supersonic cluster source. Just before the peak of an intense He pulse from the nozzle (at left), a weakly focused laser pulse strikes from the rotating metal rod. The hot metal vapor sputtered from the surface is swept down the condensation channel in dense He, where cluster formation occurs through nucleation. The gas pulse expands into vacuum, with a skinned portion to serve as a collimated cluster bean. The deflection magnet is used to measure magnetic properties, while the final chaiber at right is for measurement of the cluster distribution by laser photoionization time-of-flight mass spectroscopy.

Figure 5a. Variation in the magnetic properties of metal clusters are investigated by measuring the depletion of a highly collimated cluster beam by an inhomogeneous magnetic field, A1 clusters at zero and high field, showing that only small clusters are appreciably deflected.

Large platinum carbonyl clusters have been investigated as models for the adsorption of carbon monoxide on platinum surfaces and on platinum electrodes. An issue is how large the clusters must be before they adopt the properties of the bulk metal. Teo et al. have investigated the magnetic properties of the clusters [Pt6(CO)12]2+, [Pt9(CO)18]2+, [Pt y(CO)22f+, and... 

Size and Structural Dependence of the Magnetic Properties of 3d Transition Metal Clusters. 

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