Origin of the fast magnetization tunneling in the single-molecule magnet [Ni(hmp)(tBuEtOH)Cl]4

TL;DR

This study investigates the origin of rapid magnetization tunneling in a single-molecule magnet, revealing that a 4th-order transverse crystal-field interaction causes significant tunnel-splitting, linked to single-ion anisotropy parameters.

Contribution

It demonstrates that the fast tunneling in Ni-based single-molecule magnets is due to 4th-order crystal-field effects, connecting microscopic anisotropy to macroscopic tunneling behavior.

Findings

Fast magnetization tunneling is caused by 4th-order transverse crystal-field interaction.

The tunnel-splitting is approximately 10 MHz for the ground state.

The anisotropy parameters relate to single-ion interactions at NiII sites.

Abstract

We present high-frequency angle-dependent EPR data for crystals of [NixZn1-x(hmp)(t-BuEtOH)Cl]4 (x = 1 and 0.02). The x = 1 complex behaves as a single-molecule magnet at low temperatures, displaying hysteresis and exceptionally fast magnetization tunneling. We show that this behavior is related to a 4th-order transverse crystal-field interaction, which produces a significant tunnel-splitting (~10 MHz) of the ground state of this S = 4 system. The magnitude of the 4th-order anisotropy, and the dominant axial term (D), can be related to the single-ion interactions (Di and Ei) at the individual NiII sites, as determined for the x = 0.02 crystals.