Breaking the ring: ⁵³Cr-NMR on the Cr₈Cd molecular nanomagnet

An accurate experimental characterization of finite antiferromagnetic (AF) spin chains is crucial for controlling and manipulating their magnetic properties and quantum states for potential applications in spintronics or quantum computation. In particular, finite AF chains are expected to show a different magnetic behaviour depending on their length and topology. Molecular AF rings are able to combine the quantum-magnetic behaviour of AF chains with a very remarkable tunability of their topological and geometrical properties. In this work we measure the ⁵³Cr-NMR spectra of the Cr₈Cd ring to study the local spin densities on the Cr sites. Cr₈Cd can in fact be considered a model system of a finite AF open chain with an even number of spins. The NMR resonant frequencies are in good agreement with the theoretical local spin densities, by assuming a core polarization field A _C = -12.7 T μ _B ^-1. Moreover, these NMR results confirm the theoretically predicted non-collinear spin arrangement along the Cr₈Cd ring, which is typical of an even-open AF spin chain.