Electrical Detection of Magnetic Perturbations through the Magnetoelectric Effect of a Molecular Spin Triangle

Dielectric and magnetoelectric (ME) studies were conducted on polycrystalline samples of the molecular spin triangle [Fe₃O(O₂CPh)₆(py)₃]ClO₄·py (Fe₃) and on its diamagnetic isostructural Ga^III analogue (Ga₃). Dielectric studies revealed a thermally activated process between approximately 15-60 K, attributed to the freezing-unfreezing of the crystallographically disordered pyridine solvates, with a paraelectric behavior above ∼68 K. Magnetoelectric studies revealed a second-order ME effect for Fe₃, which remained significant above liquid-nitrogen temperatures. Similar experiments on Ga₃ allowed to control for the instrumental baseline response and to confirm the origin of the signal as the ME effect of Fe₃. The thermal evolution of the ME coupling coefficient (α_ME) showed no discontinuities around the temperature of the freezing-unfreezing processes, indicating that it is unrelated to them. These latter are assigned the disordered-diamagnetic sublattice consisting of the pyridine solvates and perchlorate counteranions. In turn, the ME coupling is assigned to the ordered-magnetic sublattice consisting of the Fe₃ trinuclear cations. These results demonstrate that Fe₃ can directly transform magnetic perturbations to electric signals at the single-molecule level, without the need of structural transformations or long-range magnetic ordering.