Discovery of a Dysprosium Metallocene Single-Molecule Magnet with Two High-Temperature Orbach Processes

Magnetic bistability in single-molecule magnets (SMMs) is a potentialbasis for new types of nanoscale information storage material. The standard model forthermally activated relaxation of the magnetization in SMMs is based on the occurrenceof a single Orbach process. Here, we show that incorporating a phosphorus atom into theframework of the dysprosium metallocene [(CpiPr5)Dy(CpPEt4)]+[B(C6F5)4]-(CpiPr5ispenta-isopropylcyclopentadienyl, CpPEt4is tetraethylphospholyl) leads to the occurrenceof two distinct high-temperature Orbach processes, with energy barriers of 1410(10) and747(7) cm-1, respectively. These barriers provide experimental evidence for two differentspin-phonon coupling regimes, which we explain with the aid of ab initio calculations.The strong and highly axial crystalfield in this SMM also allows magnetic hysteresis to beobserved up to 70 K, using a scan rate of 25 Oe s-1. In characterizing this SMM, we showthat a conventional Debye model and consideration of rotational contributions to the spin-phonon interaction are insufficient to explain the observed phenomena