SMM-ET: An SMM Evaluation Tool for the Quantitative Treatment of Ac Susceptibility and Magnetic Hysteresis Data

Abstract

Ac susceptometry and magnetic hysteresis studies are the two most used techniques for the basic characterization of magnetic relaxation properties of Single-Molecule Magnets. Nevertheless, the full quantitative treatment of such studies is rarely carried out, in particular as regards the absolute magnitudes of the in-phase (χʹ) and out-of-phase (χʺ) ac susceptibility signals, and the exact shapes of hysteresis loops. To facilitate such quantitative analyses, an SMM evaluator tool has been developed. It uses the dc magnetic susceptibility/magnetization properties of any SMM, and the parameters characteristic of the various relevant relaxation processes (Orbach, Raman, Direct, QTM) to calculate the exact ac susceptibility/magnetic hysteresis curves under any temperature, magnetic field and ac frequency or dc field scan rate. It also implements a model that calculates the actual fraction of molecules that contribute to the SMM effect, as well as models which account for distributions of the relaxation times. Indicative examples of a "strong", a "medium" and a "weak" SMM are analysed with this tool, demonstrating the additional information that can be extracted by quantitative treatment of such data.

Fe–Gd Ferromagnetic Cyclic Coordination Cluster [FeIII4GdIII4(teaH)8(N3)8(H2O)] with Magnetic Anisotropy─Theory and Experiment

“…These loops are temperature-dependent, but sweep-rate-independent (Figure ). , If the relaxation data are plotted as an Arrhenius curve, a barrier to magnetization reversal of 9.4 K and a pre-exponential factor of 10 –13 s can be extracted (Figure S3, right). Although the latter corresponds to a higher rate than generally observed for typical SMMs, it is by no means exceptional, and may, e.g., result from the high density of excited states in 2-Gd .…”