“Isolated” DyO+ Embedded in a Ceramic Apatite Matrix Featuring Single‐Molecule Magnet Behavior with a High Energy Barrier for Magnetization Relaxation

Meeting the challenges of Moore's Law, predicting ambitious miniaturization rates of integrated circuits, requires to go beyond the traditional top‐down approaches, and to employ synthetic chemistry methods, to use bottom‐up techniques. During the recent decades, it has been shown that open‐shell coordination compounds may exhibit intramolecular spontaneous magnetization, thus offering promising prospects for storage and processing of digital information. Against this background we regarded it rewarding to implement similar magnetic centers into a ceramic material, which would provide better long‐term mechanical and chemical durability. Here we present new robust inorganic compounds containing separate DyO⁺ ions in an apatite matrix, which behave like single‐molecule magnets. The materials exhibit a blocking temperature of 11 K and an energy barrier for spin reversal of a thousand inverse centimeters which is among the highest values ever achieved.     

Solvent Responsive Magnetic Dynamics of a Dinuclear Dysprosium Single‐Molecule Magnet

A new dysprosium(III) phosphonate dimer {Dy(notpH₄)(NO₃)(H₂O)}₂ ? 8 H₂O ( 1 ) [notpH₆=1,4,7‐triazacyclononane‐1,4,7‐triyl‐tris(methylenephosphonic acid)] that contains two equivalent Dy^III ions with a three‐capped trigonal prism environment is reported. Complex 1 can be transformed into {Dy(notpH₄)(NO₃)(H₂O)}₂ ( 2 ) in a reversible manner by desorption and absorption of solvent water at ambient temperature. This process is accompanied by a large dielectric response. Magnetic studies reveal that both 1 and 2 show thermally activated magnetization relaxation as expected for single‐molecule magnets. Moreover, the magnetic dynamics of the two compounds can be manipulated by controlling the number of solvent molecules at room temperature.     

161Dy Time‐Domain Synchrotron Mössbauer Spectroscopy for Investigating Single‐Molecule Magnets Incorporating Dy Ions

Time‐domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of ¹⁶¹Dy has been used to investigate the magnetic properties of a Dy^III‐based single‐molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy₃PO)₂(H₂O)₅]Br₃?2 (Cy₃PO)?2 H₂O?2 EtOH is with B₀=582.3(5) T significantly larger than that of the free‐ion Dy^III with a ⁶H_15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the Dy^III ion. This study demonstrates that ¹⁶¹Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy‐containing compounds.     

Hyperfine‐Interaction‐Driven Suppression of Quantum Tunneling at Zero Field in a Holmium(III) Single‐Ion Magnet

An extremely rare non‐Kramers holmium(III) single‐ion magnet (SIM) is reported to be stabilized in the pentagonal‐bipyramidal geometry by a phosphine oxide with a high energy barrier of 237(4) cm⁻¹. The suppression of the quantum tunneling of magnetization (QTM) at zero field and the hyperfine structures originating from field‐induced QTMs can be observed even from the field‐dependent alternating‐current magnetic susceptibility in addition to single‐crystal hysteresis loops. These dramatic dynamics were attributed to the combination of the favorable crystal‐field environment and the hyperfine interactions arising from ¹⁶⁵Ho (I =7/2) with a natural abundance of 100 %.     

A Dysprosium Metallocene Single‐Molecule Magnet Functioning at the Axial Limit

Abstraction of a chloride ligand from the dysprosium metallocene [(Cp^ttt)₂DyCl] ( 1_Dy Cp^ttt=1,2,4‐tri(tert ‐butyl)cyclopentadienide) by the triethylsilylium cation produces the first base‐free rare‐earth metallocenium cation [(Cp^ttt)₂Dy]⁺ ( 2_Dy ) as a salt of the non‐coordinating [B(C₆F₅)₄]⁻ anion. Magnetic measurements reveal that [ 2_Dy ][B(C₆F₅)₄] is an SMM with a record anisotropy barrier up to 1277 cm⁻¹ (1837 K) in zero field and a record magnetic blocking temperature of 60 K, including hysteresis with coercivity. The exceptional magnetic axiality of 2_Dy is further highlighted by computational studies, which reveal this system to be the first lanthanide SMM in which all low‐lying Kramers doublets correspond to a well‐defined M_J value, with no significant mixing even in the higher doublets.