High frequency EPR on dilute solutions of the single molecule magnet Ni$_4$

TL;DR

This study uses high frequency EPR to analyze dilute Ni$_4$ single molecule magnets, revealing well-defined absorption peaks, spin transition details, and an upper bound on spin coherence time, advancing understanding of their quantum properties.

Contribution

It demonstrates high frequency EPR on dilute Ni$_4$ solutions, identifying spin transitions and estimating Hamiltonian parameters, with implications for quantum coherence studies.

Findings

Well-defined EPR peaks despite random orientation

Hamiltonian parameters close to single crystal values

Upper bound of ~50 ns on spin coherence time

Abstract

Dilute frozen solutions of the single molecule magnet Ni$_4$ (S=4) have been studied using high frequency D-band (130 GHz) EPR. Despite the random orientation of the molecules, well defined EPR absorption peaks are observed, due to the strong variation of the splittings between the different spin-states on magnetic field. Temperature dependent studies above 4 K and comparison with simulations enable identification of the spin transitions and determination of the Hamiltonian parameters. The latter are found to be close to those of Ni$_4$ single crystals. No echo was detected from Ni$_4$ in pulsed experiments, which sets an upper bound of about 50 ns on the spin coherence time.