Magnetic long-range order induced by quantum relaxation in single-molecule magnets

TL;DR

This study demonstrates that quantum tunneling in single-molecule magnets can induce long-range magnetic order at low temperatures through magnetic interactions, with relaxation involving spin-lattice coupling.

Contribution

It provides experimental evidence that quantum relaxation via MQT can establish long-range order in SMMs, highlighting the role of spin-lattice coupling in this process.

Findings

Magnetic order observed at low temperatures in Mn4 SMMs

Quantum tunneling facilitates long-range magnetic interactions

Spin-lattice coupling involved in quantum relaxation

Abstract

Can magnetic interactions between single-molecule magnets (SMMs) in a crystal establish long-range magnetic order at low temperatures deep in the quantum regime, where the only electron spin-fluctuations are due to incoherent magnetic quantum tunneling (MQT)? Put inversely: can MQT provide the temperature dependent fluctuations needed to destroy the ordered state above some finite Tc, although it should basically itself be a T-independent process? Our experiments on two novel Mn4 SMMs provide a positive answer to the above, showing at the same time that MQT in the SMMs has to involve spin-lattice coupling at a relaxation rate equaling that predicted and observed recently for nuclear spin-mediated quantum relaxation.