Ab Initio Prediction of Tunneling Relaxation Times and Effective Demagnetization Barriers in Kramers Lanthanide Single-Molecule Magnets

Abstract

Single-molecule magnets (SMMs) are promising candidates for molecule-based quantum information devices. Their main limitation is their cryogenic operative temperature. To achieve devices performing at higher temperatures, demagnetization mechanisms must be suppressed by chemical tuning. Electronic structure calculations can provide useful information to rationalize SMM behavior, but they do not provide a direct prediction for the key experimental parameters describing magnetic relaxation (i.e., tunneling relaxation time (τ) and effective demagnetization barrier ( U)). In this Letter, a first-principles model is proposed to predict τ and U for mononuclear, half-integer spin SMMs, allowing direct comparison with experiment. Model accuracy was assessed against experimental data for 18 mononuclear Ln complexes (15 Dy and 3 Er) and applied to 3 of the current best-performing SMMs, correctly predicting nontrivial relaxation pathways. The model shows that the combination of single-ion anisotropy and spin-spin dipolar coupling can account for the major part of tunneling demagnetization for the studied systems.

Magnetization Slow Dynamics in Ferrocenium Complexes

“…On the other hand, quantum tunneling contribution is kept in the analysis as spin-spin dipolar interactions might be relevant in these compounds. [47] Thus, Equation 1m ay be simplified to only three terms, as shown in Equation 2:…”

“…Moreover, an Orbach‐like mechanism should not be considered for this system as it possesses an isolated S= 1/2 Kramers doublet ground state, that is, a two‐level scheme, for which an energy barrier cannot be defined. On the other hand, quantum tunneling contribution is kept in the analysis as spin‐spin dipolar interactions might be relevant in these compounds . Thus, Equation 1 may be simplified to only three terms, as shown in Equation : …”

Homochiral Dysprosium Phosphonate Nanowires: Morphology Control and Magnetic Dynamics

“…Recently, Aravena et al [41–43] . proposed a new method for the prediction of effective demagnetization barriers ( U eff ) considering all state energies and their contributions to the tunneling rate.…”

“…The most important KD contribution to U eff is KD 3 for S ‐1 , and the most two important KDs contributions to U eff are KD 3 and KD 4 for S ‐3 . According to the equations S1–S3, [41–43] we calculated the U eff of individual Dy III fragments for S ‐1 and S ‐3 . The calculated saturation U eff for individual Dy III fragments of S ‐1 and S ‐3 are 225.2 and 375.5 cm −1 , respectively, which are actually not available in experimental observation since a least temperature of ca.…”

Design of high-temperature f-block molecular nanomagnets through the control of vibration-induced spin relaxation

“…Contributions from spin-spin dipole coupling to U eff and s can be incorporated by resorting to recent rstprinciples models. 15 Since the barrier height may increase from lanthanides to actinides due to a stronger ligand eld, and given the challenging computational nature of the U 3+ ion, 16,17 we propose to evaluate the effectiveness of bis-metallocenium ligands on actinides and test the efficiency of our method on the hypothetical analog [U(Cp ttt ) 2 ] + of [Dy(Cp ttt ) 2 ] + , which holds the latest record for the blocking temperature. 3 To assess the validity in SIMs with ligands of a different nature, we also apply this method to the experimentally studied uranium-based SIM UTp 3 (Tp À ¼ trispyrazolylborate) in order to rationalize its poor performance.…”