Abstract
Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal in the design of new molecules with evermore realizable applications in spin-based devices. For single-ion lanthanide systems, with strong spin–orbit coupling, the potential applications are linked to the energetic structure of the crystal field levels and quantum tunneling within the ground state. Structural engineering of the timescale of these tunneling events via appropriate design of crystal fields represents a fundamental challenge for the synthetic chemist, since tunnel splittings are expected to be suppressed by crystal field environments with sufficiently high-order symmetry. Here, we report the long missing study of the effect of a non-linear (C4) to pseudo-linear (D4d) change in crystal field symmetry in an otherwise chemically unaltered dysprosium complex. From a purely experimental study of crystal field levels and electronic spin dynamics at milliKelvin temperatures, we demonstrate the ensuing threefold reduction of the tunnel splitting.
Highlights
Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal in the design of new molecules with evermore realizable applications in spin-based devices
A free lanthanide ion exhibits strong spin–orbit coupling and has a Russell–Saunders (RS) ground multiplet characterized by a total angular momentum J, and the effect of a CF is to lift the degeneracy of the |J,mJ〉 substates of the multiplet, the total energy splitting usually being on the order of 102–103 cm−1
We report on the CF quantification and the electronic spin dynamics of the dysprosium derivatives of this family, demonstrating and quantifying the effect of an increase in point group symmetry on the ground state tunnel splitting for an otherwise unaltered lanthanide complex
Summary
Total control over the electronic spin relaxation in molecular nanomagnets is the ultimate goal in the design of new molecules with evermore realizable applications in spin-based devices. Suppression of tunneling in the bulk has been a key target in the design of new molecular nanomagnets, especially those based on single lanthanide ions[19] This desire arises from the wish to enhance the superparamagnet-like behavior of this class of molecules[20] resulting from thermally activated spin-lattice relaxation (SLR) known as Orbach relaxation[21] (a resonant spin–phonon interaction involving an excited crystal field (CF) state). We report on the CF quantification and the electronic spin dynamics of the dysprosium derivatives of this family, demonstrating and quantifying the effect of an increase in point group symmetry (from non-linear C4 to pseudo-linear idealized D4d within a 1 % error bar) on the ground state tunnel splitting for an otherwise unaltered lanthanide complex
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