Pressure-Induced Conversion of a Paramagnetic FeCo Complex into a Molecular Magnetic Switch with Tuneable Hysteresis.

A key challenge in the design of magnetic molecular switches is to obtain bistability at room temperature. Here, we show that a moderate pressure allows converting a paramagnetic Fe III 2 Co II 2 square complex into a molecular switch exhibiting a full dia- to para-magnetic transition: Fe II Co III ⬄ Fe III Co II . Moreover, the complex follows a rare behavior: the higher the pressure is, the broader the magnetic hysteresis is. Thus, the application of an adequate pressure allows inducing a magnetic bi-stability at room temperature with predictable hysteresis width. The structural studies at different pressures suggest that the pressure-enhanced bi-stability is due to the strengthening of intermolecular interactions upon pressure increase. An original microscopic Ising-like model including pressure effects, is developed to simulate this unprecedented behavior. Overall, this study shows that FeCo complexes could be very sensitive piezo-switches with potential use as sensors.