Unconventional Nuclear-Spin-Dependent Toroidal Ground States in Isotopologue ^ADy₄ [2 × 2] Complexes

Area of Science:

• Quantum Chemistry and Materials Science
• Spintronics and Quantum Computing

Background:

• Understanding nuclear spin effects on electronic spin relaxation in single-molecule magnets (SMMs) is crucial for quantum technology.
• The influence of nuclear spins on relaxation dynamics in Single Molecule Toroidal (SMT) systems remains largely unexplored.

Purpose of the Study:

• To investigate the impact of nuclear spins on the relaxation dynamics of isotopically enriched Dy4 grid complexes.
• To explore the role of hyperfine coupling in modulating quantum tunneling of magnetization (QTM) and toroidal states.

Main Methods:

• Synthesized and studied two isotopologues: 164Dy4L4 (I=0) and 163Dy4L4 (I=5/2).
• Utilized cryogenic μSQUID magnetometry down to 30 mK.
• Performed ab initio calculations and spin-Hamiltonian modeling.

Main Results:

• Both isotopologues exhibited a pseudotoroidal ground state with hexagonal angular maps and S-shaped hysteresis loops.
• 164Dy4L4 showed sharp QTM transitions, while 163Dy4L4 displayed altered dynamics due to hyperfine coupling.
• Contrary to expectations, nuclear spins in 163Dy4L4 did not accelerate relaxation but promoted population transfer, slowing dynamics and increasing hysteresis.

Conclusions:

• Nuclear spins exert a constructive, nonintuitive influence on toroidal SMMs, offering a new control mechanism for low-temperature relaxation.
• Isotopically controlled lanthanide assemblies are promising platforms for studying quantum phenomena and molecular information processing.