Magnetic Relaxation of Lanthanide-Based Molecular Magnets

Giant exchange coupling and field-induced slow relaxation of magnetization in Gd2@C79N with a single-electron Gd–Gd bond

“…14 However, if the number of spins is much larger than the number of resonant phonons, the energy dissipation is hampered resulting in a phonon bottleneck, 15 which elongates the relaxation with complex temperature dependence ( τ m –1 ∼ T b , 1 ≤ b ≤ 4). 16 Finally, the Raman mechanism with τ m –1 ∼ T 9 dependence for Kramers systems is plausible at higher temperatures. 14 Thus, the value of n = 3.2 determined for Gd 2 @C 79 N may be an indication of the bottlenecked direct relaxation mechanism near 2 K, but in the view of significant uncertainties of the values this conclusion remains tentative.…”

Magnetization relaxation in the single-ion magnet DySc2N@C80: quantum tunneling, magnetic dilution, and unconventional temperature dependence

“… 6 , 12 – 16 Large magnetic anisotropy leads to magnetic bistability on a single-molecule level with slow relaxation of magnetization within bi-stable doublet, a phenomenon also known as single molecule magnetism. 17 – 21 Indeed, during the last five years several lanthanide, and especially Dy EMFs have been found to behave as single molecule magnets (SMMs). 6 , 16 , 22 – 29 …”

“…Extended studies of these processes laid the foundation for further understanding of SMMs. 34 – 37 With the advent of lanthanide-SMMs, 20 , 21 , 38 – 40 a diminished role of QTM might be expected. Lanthanide ions usually feature much stronger magnetic anisotropy, hence preventing avoided level crossing in the normally accessible range of magnetic fields (note that avoided level crossing is still possible for multinuclear systems, 41 or when coupling to nuclear spin can be resolved, as in Ho, 40 , 42 , 43 Tb, 44 or isotopically enriched 163 Dy compounds; 45 in such system, several QTM steps can be observed in magnetization curves at low temperatures).…”

Multifunktionale Einzelmolekülmagnete auf Lanthanoidbasis in neuem Licht

“…Derartige Prozesse – bekannt als Raman‐Prozess, direkter Prozess und Quantentunneln der Magnetisierung (QTM) – sind oft sehr nachteilig für die Relaxationsdynamik von Lanthanoid‐SMMs. Während eine ausführliche Erläuterung derartiger Prozesse außerhalb des Rahmens dieses Aufsatzes liegt, werden wir auf die enorme Bedeutung solcher Mechanismen für die gesamte Spinrelaxationsdynamik von Ln 3+ ‐SMMs eingehen [65–69] . Die Leistung eines SMM beruht sowohl auf der Elektronenstruktur des Ln 3+ ‐Ions als auch auf der Wechselwirkung des magnetischen Moments mit seiner Umgebung.…”