Transition metal clusters magnetic behavior

In molecules, the interaction of surrogate spins localized at the atomic centers is calculated describing a picture of spin-spin interaction of atoms. This picture became prominent for the description of the magnetic behavior of transition-metal clusters, where the coupling type (parallel or antiparallel) of surrogate spins localized at the metal centers is of interest. Once such a description is available it is possible to analyze any wave function with respect to the coupling type between the metal centers. Then, local spin operators can be employed in the Heisenberg Spin Hamiltonian. An overview over wave-function analyses for open-shell molecules with respect to local spins can be found in Ref. (118). 

To summarize, one can note that the magnetic characteristics of small clusters of the transition metals vary in a nonmonotonous way as a function of the number of atoms in the cluster. This nonscalable behavior is what makes small clusters interesting and complex at the same time, offering possibilities for future technological applications. 

S. N. Khanna and S. Linderoth, Magnetic Behavior of Clusters of Ferromagnetic Transition Metals, Phys. Rev. Lett. 67, 742-745 1991... 

Kumar, V., and Kawazoe, Y. 2002. Icosahedral growth, magnetic behavior, and adsorbate-induced metal-nonmetal transition in palladium clusters. Phys. Rev. B 66 144413. 

While simple metal clusters can be understood in terms of simple shell models, properties of transition metal (TM) clusters do not show any systematic size variation, and they are not describable by any simple models. However, TM clusters manifest rich and interesting magnetic behavior. Particularly interesting is the variation of their magnetic behavior with size, which provides us with an avenue to study evolution of this interesting property from the atomic to the bulk length scales. 

---