Fingerprinting molecular nanomagnets by four-dimensional inelastic neutron scattering.

Four-dimensional inelastic neutron scattering is an invaluable tool to study the spin dynamics of molecular nanomagnets. The power of the technique comes from the capability to measure the scattering cross-section over large portions of the energy-wavevector space, yielding a faithful portray of spin fluctuations on the space- and time-scales characterizing the internal dynamics of the magnetic core [1].
This can been exploited to portray and quantify entanglement in systems of weakly coupled molecular qubits, such as the (Cr₇Ni)₂ supramolecular dimer. The inelastic cross-section shows a fine structure associated with the qubut-qubit coupling, which allows one to directly extract the quantum concurrence in selected eigenstates [2].
In a recent application to the archetypal Mn₁₂ nanomagnet [3], cross-section data of high quality have been used to pinpoint the eigenstates of the spin Hamiltonian. In this way, the values of exchange constants have been identified univocally.

[1] Spin dynamics of molecular nanomagnets unravelled at atomic scale by four-dimensional inelastic neutron scattering, M. L. Baker, T. Guidi, S. Carretta, J. Ollivier, H. Mutka, H. U. Güdel, G. A. Timco, Eric J. L. McInnes, G. Amoretti, R. E. P.Winpenny, P. Santini, Nat. Phys 8, 906 (2012).
[2] Portraying entanglement between molecular qubits with four-dimensional inelastic neutron scattering, E. Garlatti, T. Guidi, S. Ansbro, P. Santini, G. Amoretti, J. Ollivier, H. Mutka, G. Timco, I.J. Vitorica-Yrezabal, G.F.S. Whitehead, R.E.P. Winpenny, S. Carretta, Nat. Commun. 8, 14543 (2017).
[3] Magnetic exchange interactions in the molecular nanomagnet Mn₁₂, A. Chiesa, T. Guidi, S. Carretta, S. Ansbro, G. A. Timco, I. Vitorica-Yrezabal, E.Garlatti, G. Amoretti, R. E. P. Winpenny, and P. Santini, Phys. Rev. Lett. in press (2017).