Hilbert Space in Isotopologue Dy(III) SMM Dimers: Dipole Interaction Limit in [^163/164Dy₂(tmhd)₆(tape)]⁰ Complexes

Abstract

Single-molecule magnets are molecular complexes proposed to be useful for information storage and quantum information processing applications. In the quest for multilevel systems that can act as Qu<i>d</i>its, two dysprosium-based isotopologues were synthesized and characterized. The isotopologues are [¹⁶⁴Dy₂(tmhd)₆(tape)] (<b>1</b>^(<i>I</i>=0)) and [¹⁶³Dy₂(tmhd)₆(tape)] (<b>2</b>^{(<i>I</i><b>=</b>5/2)}), where tmhd = 2,2,6,6-tetramethylheptandionate and tape = 1,6,7,12-tetraazaperylene. Both complexes showed slow relaxation at a zero applied magnetic field with dominant Orbach and Raman relaxation mechanisms. μSQUID studies at milli-Kelvin temperatures reveal quasi-single ion loops, in contrast with the expected S-shape (near zero field) butterfly loops, characteristic of antiferromagnetically coupled dimeric complexes. Through analysis of the low-temperature data, we find that the interaction operating between Dy(III) is small, leading to a small exchange biasing from the zero-field transition. The resulting indirectly coupled nuclear states are degenerate or possess a small energy difference between them. We, therefore, conclude that for the creation of Qu<i>d</i>its with enlarged Hilbert spaces, shorter Dy(III)···Dy(III) distances are deemed essential.