Relevance of Dzyaloshinskii–Moriya spectral broadenings in promoting spin decoherence: a comparative pulsed-EPR study of two structurally related iron(iii) and chromium(iii) spin-triangle molecular qubits

Spectral broadenings due to Dzyaloshinskii-Moriya interactions (DMI) were assessed with respect to the decoherence they induce through increased spin-spin interactions, as the role of DMI in developing magnetoelectric spin-chirality qubits is gaining recognition. The structurally related spin triangles [Fe 3 O(PhCOO) 6 (py) 3 ]ClO 4 ·py (Fe 3 ) and [Cr 3 O(PhCOO) 6 (py) 3 ]ClO 4 ·0.5py (Cr 3 ) were studied as frozen py-d 5 solutions with various pulsed Electron Paramagnetic Resonance (EPR) spectroscopy experiments, and under identical experimental conditions. Field-swept Hahn echo experiments revealed a match with continuous-wave (CW) spectra, while variable-temperature saturation/inversion recovery and Hahn echo decay experiments were used to extract the thermal evolutions of the spin-lattice relaxation and phase-memory times (T 1 and T m , respectively). Nutation experiments revealed Rabi oscillations demonstrating that the spins of the complexes could be coherently manipulated. Careful comparisons of T m imes confirmed hyperfine interactions with the magnetic nuclei of the metal ions as an intrinsic source of decoherence. Comparisons of Rabi damping times revealed that DMI-induced spectral broadenings play a discernible but moderate role as an extrinsic source of decoherence for the nutation experiments and that they are not particularly detrimental to spin manipulations.