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Abstract: Continuous wave (cw) and pulsed high frequency electron paramagnetic resonance (HF-EPR) measurements were performed on an Fe-based magnetic cluster: Fe7O4(O2CPh)11(dmem)2, abbreviated Fe7. The cw EPR results show that two different molecular species exist in the crystal, with slightly different zero-field-splitting parameters. The spin decoherence time, T 2, was measured at high magnetic fields and low temperatures, which makes it possible to obtain high spin polarization and to significantly reduce decoherence due to electron spin flip-flop processes. Theoretical fitting of T 2 versus temperature shows that, for crystalline samples of this molecule, spin flip-flop fluctuations represent the main source of spin decoherence at low temperatures, as reported also for the Fe8 single-molecule magnet [Phys. Rev. Lett. 102 (2009) 087603]. Moreover, it is found that T 2 is position dependent within the EPR line, a model for which is given. We also note that this is the third example of an Fe-based cluster that exhibits a measurable decoherence time, and only the second involving a crystal. [Copyright &y& Elsevier]

Qubits are the basic unit of quantum information and computation. To realize quantum computing and information processing, the decoherence times of qubits must be long enough. Among the studies of molecule‐based electron spin qubits, most of the work focused on the ions with the spin S=1/2, where only single‐bit gates can be constructed. However, quantum operations require the qubits to interact with each other, so people gradually carry out relevant research in ions or systems with S>1/2 and multilevel states. In this work, a two‐dimensional (2D) oxygen‐coordinated GdIIINaI‐based oxamato supramolecular coordination framework, Na[Gd(4‐HOpa)4(H2O)] ⋅ 2H2O (1, 4‐HOpa=N‐4‐hydroxyphenyloxamate), was selected as a possible carrier of qubit. The field‐induced slow magnetic relaxation shows this system has phonon bottleneck (PB) effect at low temperatures with a very weak magnetic anisotropy. The pulse electron paramagnetic resonance studies show the spin‐lattice and spin‐spin relaxation times are T1=1.66 ms at 4 K and Tm=4.25 μs at 8 K for its diamagnetically diluted sample (1Gd0.12 %). It suggested that the relatively long decoherence time is mainly ascribed to its near isotropic and the PB effect from resonance phonon trapped for pure sample, while the dilution further improves its qubit performance. [ABSTRACT FROM AUTHOR]