Michael L. Baker, Tatiana Guidi, Stefano Carretta, Jacques Ollivier, Hannu Mutka, Hans U. Güdel, Grigore A. Timco, Eric J. L. McInnes, Giuseppe Amoretti, Richard E. P. Winpenny and Paolo Santini
Spin dynamics of molecular nanomagnets unravelled at atomic scale by four-dimensional inelastic neutron scattering
Nature Physics 8, 906-911 (2012)                 
( see also:  Nature Physics 8, 859-860 (2012)               )

Abstract: Molecular nanomagnets are among the first examples of finite-size spin systems and have been test beds for addressing several phenomena in quantum dynamics. In fact, for short-enough timescales the spin wavefunctions evolve coherently according to an appropriate spin Hamiltonian, which can be engineered to meet specific requirements. Unfortunately, so far it has been impossible to determine these spin dynamics directly. Here we show that recently developed instrumentation yields the four-dimensional inelastic-neutron scattering function in vast portions of reciprocal space and enables the spin dynamics to be determined directly. We use the Cr₈ antiferromagnetic ring as a benchmark to demonstrate the potential of this approach which allows us, for example, to examine how quantum fluctuations propagate along the ring or to test the degree of validity of the Néel-vector-tunnelling framework.