The up-or-down spin of an electron makes it a natural qubit candidate for use, someday, in a quantum computer. Circuit logic based on the flipping of spins would require less energy and suffer far less heat dissipation than that based on the switching of charge. The challenge is to prepare the spins, flip them on cue, and then reliably read out their final states within a system—all while minimizing decoherence 1 (see Physics Today, March 2006, page 16).
Advances in the fabrication of ever-smaller structures are driving research into understanding how to meet at least part of that challenge. At atomic length scales, small numbers of spins can be coupled directly in transition-metal clusters or one-dimensional chains. Such tiny magnets are typically produced using wet chemistry or dry self-assembly. Neutron scattering, electron paramagnetic resonance, susceptibility measurements, and other diagnostics provide details about their magnetic properties, including how strongly...
