Polyanisotropic Magnetoelectric Coupling in an Electrically Controlled Molecular Spin Qubit

Two molecular spin qubits are studied with pulsed electron paramagnetic resonance (EPR) spectroscopy under electric fields to assess their magnetoelectric (ME) couplings and electric spin control. [Fe₃O­(PhCOO)₆(py)₃]­ClO₄·py (Fe₃) is characterized by strong Dzyaloshinskii–Moriya interactions (DMI) which induce important magnetoanisotropy, whereas the DMI in [Cr₃O­(PhCOO)₆(py)₃]­ClO₄·0.5py (Cr₃) is 1–2 orders of magnitude weaker. Fe₃ is observed to demonstrate a clear ME effect, whose intensity shows an unprecedented dependence on the molecular orientation within the electric field E (electroanisotropy) and on the relative orientations of the molecular z axis, the Zeeman field B₀ and E (magnetoelectric anisotropy). The electric control in Fe₃ is shown to be coherent, and the ME effect exhibits complex dynamics characterized by saturation and oscillatory effects. On the other hand, Cr₃ exhibits no discernible ME effect, which correlates well with its negligible DMI.