Magnetic Memory of a Single-molecule Quantum Magnet Wired to a Gold Surface

In the field of mol. spintronics, the use of magnetic mols. for information technol. is a main target and the observation of magnetic hysteresis on individual mols. organized on surfaces is a necessary step to develop mol. memory arrays. Although simple paramagnetic mols. can show surface-induced magnetic ordering and hysteresis when deposited on ferromagnetic surfaces, information storage at the mol. level requires mols. exhibiting an intrinsic remnant magnetization, like the so-called single-mol. magnets (SMMs). These have been intensively investigated for their rich quantum behavior but no magnetic hysteresis has been so far reported for monolayers of SMMs on various nonmagnetic substrates, most probably owing to the chem. instability of clusters on surfaces. Using X-ray absorption spectroscopy and X-ray magnetic CD synchrotron-based techniques, pushed to the limits in sensitivity and operated at sub-kelvin temps., we have now found that robust, tailor-made Fe4 complexes retain magnetic hysteresis at gold surfaces. Our results demonstrate that isolated SMMs can be used for storing information. The road is now open to address individual mols. wired to a conducting surface in their blocked magnetization state, thereby enabling investigation of the elementary interactions between electron transport and magnetism degrees of freedom at the mol. scale.