Two-Step Relaxation in a Linear Tetranuclear Dysprosium(III) Aggregate Showing Single-Molecule Magnet Behavior

Abstract

A well-defined two-step relaxation, described by the sum of two modified Debye functions, is observed in a new alkoxido-bridged linear tetranuclear Dy(III) aggregate showing single-molecule magnet behavior with a remarkably large energy barrier. This compound represents a model molecular aggregate with a clear two-step relaxation evidenced by frequency-dependent susceptibility, which therefore may stimulate further investigations regarding the relaxation dynamics of lanthanide-based systems.

Magnetic Behavior of Carboxylate and β-Diketonate Lanthanide Complexes Containing Stable Organometallic Moieties in the Core-Forming Ligand

“…The {Dy(η 2 -O2CCym)2(μ-O2CCym)4} polyhedron is strongly distorted and is most similar to a trigonal dodecahedron with the central segments of the trapezohedra occupied by η 2 -O2C moieties. It has been shown [44] that the existence of magnetic centers with differing anisotropy can give rise to two ) and 1000 Oe ( the potential barrier of magnetization reversal, ΔE/kB = 53 K, and the pre-exponential factor, τ0 = 3.2·10 −9 s. The magnetization dynamics of 2 was also studied under an applied dc magnetic field in order to minimize the probability of quantum tunneling ( Figure S5). It was found that the external magnetic field did not affect considerably the relaxation processes in Complex 2 ( Figure 10).…”

Rare earths: jewels for functional materials of the future

“…7 Increasing the nuclearity of Dy clusters seems to be beneficial to the design of SMMs as demonstrated by a tetranuclear oxo-bridged Dy III cluster which possesses two relaxation mechanisms with large energy barriers of 19.7 and 173 K (13.7 and 120 cm À1 ). 57 …”

Modulating the magnetic relaxation of lanthanide-based single-molecule magnets

“…Further, more flexible polydentate ligands could be applied for the polynuclear Lanthanide-based SMMs [34,35]. Consequently, the complicated multiple relaxation processes, which are most likely associated with distinct anisotropic centers due to the different crystal field environments, have been increasingly identified in a weakly coupled lanthanide system [20,21]. It is therefore possible to "fine-tune" the magnetic properties of lanthanide complexes through the alteration of different ligand fields.…”

“…However, theoretical study based on experiments suggests that large magnetic anisotropy is not helped by a high spin state of the ground state for transition-metal systems, which has been a crucial roadblock to obtaining systems with larger energy barriers [12,13]. Nevertheless, since Ishikawa et al [14] discovered lanthanide double-decker complexes [Pc 2 Ln] − TBA + (Ln = Tb III , Dy III , Ho III ; TBA + = N(C 4 H 9 ) + ) functioning as very efficient SMMs, the complexes containing lanthanide elements are highlighted and large numbers of Lanthanide-based Single Molecule Magnets (Ln-SMMs) with larger energy barriers have evolved, especially Dy-based complexes with various nuclearities from Dy 1 [15], Dy 2 [16,17], Dy 3 [18,19], Dy 4 [20,21], Dy 6 [22], Dy 10 [23] to Dy 26 [24]. These systems may hold the key to obtaining high anisotropic barrier single-molecule magnets (SMMs).…”