Large quantum nonlinear dynamic susceptibility of single-molecule magnets

TL;DR

This paper demonstrates that single-molecule magnets exhibit a large, quantum-driven nonlinear magnetic response that is largely unaffected by spin-lattice interactions, highlighting the importance of nonlinear susceptibility as a quantum probe.

Contribution

It reveals the significant quantum nonlinear susceptibility in single-molecule magnets and proposes it as a key tool for detecting quantum effects in mesoscopic magnetic systems.

Findings

Large nonlinear susceptibility observed experimentally.

Peaks in susceptibility are reversed compared to classical superparamagnets.

Nonlinear response is insensitive to spin-lattice coupling.

Abstract

The nonlinear dynamical response of Mn$_{12}$ single-molecule magnets is experimentally found to be very large, quite insensitive to the spin-lattice coupling constant, and displaying peaks reversed with respect to classical superparamagnets. It is shown that these features are caused by the strong field dependence of the relaxation rate due to the detuning of energy levels between which tunneling takes place. The nonlinear susceptibility technique, previously overlooked, is thus proposed as a privileged probe to ascertain the occurrence of quantum effects in mesoscopic magnetic systems.