Dr Nick Chilton: Record-breaking energy barrier to magnetisation reversal
A study published in Angewandte Chemie Int. Ed. (2016, 55, 16071) describes a highly symmetric molecule of dysprosium, with a record-breaking energy barrier to magnetic reversal of 1815(1) K, surpassing the previous record holder by ca. 800 K.
Single molecule magnets (SMMs) are molecules that display slow reversal of their magnetisation deriving purely from their molecular properties. The challenge is to obtain molecules that can retain magnetic information at high temperatures; this is closely linked to the molecule’s energy barrier to magnetisation reversal. The best-performing molecules currently operate at around 10 Kelvin, so are not commercially viable. In this Sino-Manchester collaboration of Prof. Richard Winpenny and Dr. Nicholas Chilton with Prof. Yan-Zhen Zeng and Mr. You-Song Ding (Xi'an Jiaotong University, P.R. China), the team have prepared and characterised a molecule with local pentagonal bipyramidal coordination geometry. The key structural features of this molecule are a pair of bis-trans-disposed alkoxide ligands with five neutral solvent molecules in the equatorial plane. Such molecular architectures consisting of a strong axial ligand field follow a design proposed (Chem. Commun., 2015, 51, 101; Inorg. Chem., 2015, 54, 2097) and validated (Chem. Sci., 2016, 7, 155) by work here at Manchester. By imposing a strong axial field, the electronic states of the dysprosium ion are arranged such that a very large energy barrier must be passed for the magnetisation to relax. This approach leads to magnetic memory effects at 14 K, equalling the previous record, and further confirms the Manchester blue-print for high-temperature SMMs.