Toward promising candidates of quantum information processing, the rapid development of lanthanide-based single-molecule magnets (Ln-SMMs) highlights design strategies in consideration of the local ...symmetry of lanthanide ions. In this review, crystal-field theory is employed to demonstrate the electronic structures according to the semiquantitative electrostatic model. Then, specific symmetry elements are analysed for the elimination of transverse crystal fields and quantum tunnelling of magnetization (QTM). In this way, high-performance Ln-SMMs can be designed to enable extremely slow relaxation of magnetization, namely magnetic blocking; however, their practical magnetic characterization becomes increasingly challenging. Therefore, we will attempt to interpret the experimental behaviours and clarify some issues in detail. Finally, representative Ln-SMMs with specific local symmetries are summarized in combination with the discussion on the symmetry strategies, and some of the underlying questions are put forward.
Based on crystal-field theory, design strategies in consideration of local symmetry are highlighted for lanthanide-based single-molecule magnets, accompanied by practical concerns about magnetic studies and representative cases.
Single-molecule magnets (SMMs) containing only one metal center may represent the lower size limit for molecule-based magnetic information storage materials. Their current drawback is that all SMMs ...require liquid-helium cooling to show magnetic memory effects. We now report a chemical strategy to access the dysprosium metallocene cation (Cp
)Dy(Cp*)
(Cp
, penta-iso-propylcyclopentadienyl; Cp
pentamethylcyclopentadienyl), which displays magnetic hysteresis above liquid-nitrogen temperatures. An effective energy barrier to reversal of the magnetization of
= 1541 wave number is also measured. The magnetic blocking temperature of
= 80 kelvin for this cation overcomes an essential barrier toward the development of nanomagnet devices that function at practical temperatures.
The challenge of person re-identification (re-id) is to match individual images of the same person captured by different nonoverlapping camera views against significant and unknown cross-view feature ...distortion. While a large number of distance metric/ subspace learning models have been developed for re-id, the cross-view transformations they learned are view-generic and thus potentially less effective in quantifying the feature distortion inherent to each camera view. Learning view-specific feature transformations for re-id (i.e., view-specific re-id), an under-studied approach, becomes an alternative resort for this problem. In this work, we formulate a novel view-specific person re-identification framework from the feature augmentation point of view, called Camera coRrelation Aware Feature augmenTation (CRAFT). Specifically, CRAFT performs cross-view adaptation by automatically measuring camera correlation from cross-view visual data distribution and adaptively conducting feature augmentation to transform the original features into a new adaptive space. Through our augmentation framework, view-generic learning algorithms can be readily generalized to learn and optimize view-specific sub-models whilst simultaneously modelling view-generic discrimination information. Therefore, our framework not only inherits the strength of view-generic model learning but also provides an effective way to take into account view specific characteristics. Our CRAFT framework can be extended to jointly learn view-specific feature transformations for person re-id across a large network with more than two cameras, a largely under-investigated but realistic re-id setting. Additionally, we present a domain-generic deep person appearance representation which is designed particularly to be towards view invariant for facilitating cross-view adaptation by CRAFT. We conducted extensively comparative experiments to validate the superiority and advantages of our proposed framework over state-of-the-art competitors on contemporary challenging person re-id datasets.
ion of a chloride ligand from the dysprosium metallocene (Cpttt)2DyCl (1Dy Cpttt=1,2,4‐tri(tert‐butyl)cyclopentadienide) by the triethylsilylium cation produces the first base‐free rare‐earth ...metallocenium cation (Cpttt)2Dy+ (2Dy) as a salt of the non‐coordinating B(C6F5)4− anion. Magnetic measurements reveal that 2DyB(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 2Dy 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 MJ value, with no significant mixing even in the higher doublets.
SMMashing: A dysprosium(III) metallocenium cation is a single‐molecule magnet (SMM) with a record anisotropy barrier of 1277 cm−1 and record magnetic blocking up to 60 K, including hysteresis with coercivity.
Ultra-compact X-ray binaries (UCXBs) are low-mass X-ray binaries with ultra-short orbital periods (usually less than 1 hr) and hydrogen-poor donor stars, which are proposed to be potential Laser ...Interferometer Space Antenna (LISA) sources. In this work, we first employ the Modules for Experiments in Stellar Astrophysics code to examine the parameter space of the progenitors of UCXBs that LISA will detect. Our simulations indicate that the initial binaries with a neutron star and a companion star, in an orbit of initial orbital period smaller than the bifurcation period, could evolve into UCXBs, some of which will emit gravitational wave signals that can be detectable by LISA. However, the initial orbital periods of the binaries that will evolve into UCXB-LISA sources in a distance of 10 kpc are located in a very narrow range, i.e., the formation of these LISA source requires an extreme fine-tuning of initial parameter. According to the characteristic strains and the derived maximum detectable distances, four sources among eight UCXBs with the observed distances are expected to be detected by LISA. Based on the parameter space given by the detailed binary evolution models and the rapid binary star evolution code, the birthrate of UCXBs appearing as LISA sources in the Galaxy is estimated to be . Considering the contribution of UCXBs in globular clusters, the number of UCXB-LISA sources can reach 240-320. Although the formation condition is severe, the detectability of UCXBs by LISA is still significant because it provides an opportunity to pursue full multi-messenger investigations.
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 %.
An extremely rare non‐Kramers holmium(III) single‐ion magnet is reported. The suppression of the quantum tunneling of magnetization at zero field and the hyperfine structures were observed in AC magnetic susceptibility measurements, and were attributed to the combination of a favorable crystal‐field environment and the hyperfine interactions arising from 165Ho (I=7/2) with a natural abundance of 100 %.
The scientific aim of the space gravitational-wave (GW) detector Laser Interferometer Space Antenna (LISA) that was scheduled to launch in the early 2030s is to detect the low-frequency GW signals in ...the Galaxy. Its main candidate GW sources are compact binaries of white dwarfs and neutron stars. In this work, we examine whether compact intermediate-mass black hole (IMBH) X-ray binaries could be potential LISA sources. Our simulations indicate that an IMBH binary with a 1000 M IMBH and a 3 M donor star in an initial orbital period near the so-called bifurcation period of 0.77 day could evolve into an ultra-compact X-ray binary, which will emit GW signals with a maximum frequency of 2.5 mHz. According to the evolutionary tracks of characteristic strain, IMBH X-ray binaries with the initial donor-star masses of 1-3 M and the initial orbital periods slightly less than the bifurcation periods will be detectable by the LISA in a distance of 15 kpc. Assuming each of 60 Galactic globular clusters hosts a 1000 M IMBH, the maximum number of compact IMBH X-ray binaries that LISA will detect in the Galaxy should be less than ten. Therefore, the detectability of compact IMBH X-ray binaries by the LISA is not optimistic.
Manipulating bistability at the molecular level, especially in single-molecule magnet (SMM) and spin-crossover (SCO) materials, has attracted enormous recent interest due to their multifaceted ...magnetic behaviour and potential applications in devices. Moreover, their fascinating properties can be further modulated
via
chemical modifications and external stimuli, bringing about vast possibilities and valuable lessons. In this Feature Article, we present a selection of our research into this topic, as well as some other related achievements that have been made in recent years.
In this Feature Article, we summarize the recent progress made in modulating the multifaceted magnetic behaviour of single-molecule magnets (SMMs) and spin-crossover (SCO) materials based on chemical modifications and external stimuli.
A general and practical approach for diverse dealkenylative functionalization of olefin‐containing substrates has been developed through the one‐pot formation and utilization of pro‐aromatic ...1,4‐dihydropyridazines using tetrazine as the key cycloaddition reagent. Triggered by either excitation or oxidation, the targeted C−C bonds in the 1,4‐dihydropyridazine intermediates could be readily cleaved to generate alkyl radicals for subsequent transformations. Diverse carbon‐carbon and carbon‐hetero bond forming protocols, including Giese‐type addition, hydrazination, borylation, Minisci‐type alkylation, copper‐catalyzed NH alkylation, acylation, alkynylation, cyanation, and azidation, are achieved in a highly modular fashion.
Dealkenylative Giese‐type addition, hydrazination, borylation, Minisci‐type alkylation, copper‐catalyzed NH alkylation, acylation, alkynylation, cyanation, and azidation, have been achieved on olefin‐containing substrates in a one‐pot and highly modular fashion.
A stable site‐isolated mononuclear platinum catalyst with a well‐defined structure is presented. Platinum complexes supported in zeolite KLTL were synthesized from Pt(NH3)4(NO3)2, oxidized at 633 K, ...and used to catalyze CO oxidation. IR and X‐ray absorption spectra and electron micrographs determine the structures and locations of the platinum complexes in the zeolite pores, demonstrate the platinum‐support bonding, and show that the platinum remained site isolated after oxidation and catalysis.
In the right spot: A site‐isolated mononuclear platinum catalyst is supported in the zeolite KLTL with a stable and well‐defined structure. This catalyst was examined spectroscopically and imaged with STEM (see picture) to show locations of the platinum complexes (blue circles) within the zeolite pores.
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