Magnetoelastic Instability in Ring-Shaped Molecule Magnets with Next-Nearest Neighbor Coupling

In considering next-nearest neighbor （NNN） coupling, we numerically investigate the magnetoelastic instability in ring-shaped mesoscopic antiferromagnetic Heisenberg spin 1/2 systems with spin-phonon interaction. The results indicate that, for antiferromagnetic NNN coupling J2, there may be a critical value J2^c, at which the ground state is dimerized for arbitrary lattice spring constant and beyond and below which the magnetoelastic instability behavior is different from each other. The values of J2^c are irrelevant to the system size. For ferromagnetic NNN coupling, only continuous transition is present from dimerized phase to uniform phase as lattice spring constant is increased.

Deterministic Generation of Quantum State Transfer Between Spatially Separated Single Molecule Magnets

We propose a new scheme for realizing deterministic quantum state transfer （QST） between two spatially separated single molecule magnets （SMMs） with the framework of cavity quantum eleetrodynamics （QED）. In the present scheme, two SMMs are trapped in two spatially separated optical cavities coupled by an optical fiber. Through strictly numerically simulating, we demonstrate that our scheme is robust with respect to the SMMs＇ spontaneous decay and fiber loss under the conditions of dispersive SMMs-field interaction and strong coupling of cavity fiber. In addition, we also discuss the influence of photon leakage out of cavities and show that our proposal is good enough to demonstrate the generation of QST with high fidelity utilizing the current experimental technology. The present investigation provides research opportunities for realizing QST between solid-state qubits and may result in a substantial impact on the progress of solid-state-based quantum communications network.

Anisotropic magnetocaloric effect in a dysprosium(Ⅲ) single-molecule magnet——Commemorating the 100th anniversary of the birth of Academician Guangxian Xu

Dysprosium compounds with high magnetic anisotropy are widely studied as single molecule magnets(SMMs).Here the anisotropic magnetocaloric effect in a Dy(Ⅲ)SMM,{[Dy(OSiMe_(3))_(2)(4-Mepy)5(BPh_(4))]0.5 Toluene},was studied by single crystals.Angular dependent magnetization can be observed at 300 K because of its high magnetic anisotropy.SMM behavior measured along the easy axis direction is identical to that of the polycrystalline sample.Rotating magnetization from the easy axis to the hard plane gives a maximum magnetic entropy change(-ΔSR)of 3.05 J/(kg·K)at 19 K atΔB=5 T,which enables the Dy(Ⅲ)SMM to be used as a low-temperature rotating magnetic refrigerant.

Single molecule magnetic behavior and photo-enhanced proton conductivity in a series of photochromic complexes

Molecules with multifunctional properties are of immense interest in hybrid materials, while challenges still existed because of the limited compatibility of multiple functionalities in a single system. In this work, a series of metal-organic complexes were synthesized and characterized under the assembly of electron donor phosphonate, electron acceptor polypyridine ligand and spin carrier rare earth ions. All the compounds exhibited remarkable and reversible responses with photochromism and photomodulated fluorescence, originated from photogenerated radicals via electron transfer from phosphonates to polypyridine ligands. For the Dy analog, slow magnetic relaxation was observed at cryogenic temperature, indicating the single-molecule magnetic behavior. Furthermore, photogenerated radicals could enhance the proton conductive behavior, with about 2 times larger in magnitude after light irradiation for Dy and Y compounds. The introduction of photoluminescence, magnetism and proton conduction into metallic phosphonates can provide potential applications for photochromic materials.

Calixarene-supported hexadysprosium cluster showing single molecule magnet behavior

The syntheses, crystal structures, magnetic and luminescent properties of three isornorphous compounds [LnIII6（,u4-O）2（C4A）2- （NO3）2（HCOO）2（CH30）2（DMF）4（CH3OH）4] （Ln = Gd （1）, Tb （2） and Dy （3）; H4C4A = p-tert-butylcalix[4]arene） are reported. These three compounds are featured with the sandwich-like units constructed by two tail-to-tail calixarene molecules and an in-between Lnm6 octahedron. The DyTM compound exhibits both single molecule magnet behavior and photoluminescence.

Cyanide-bridged single molecule magnet based on a manganese(Ⅲ) complex with TTF-fused Schiff base ligand

Reaction of [Mn（TTF-salphen）][OAc] （TTF-salphen2=2,2＇-（（2-（4,5-bis（methylthio）-1,3-dithiol-2-ylidene）-1,3-benzodithiole- 5,6-diyl）bis（nitrilomethylidyne）bis（pbenolate）dianion） and the cyanometalate building blocks [n-Bu4N][（Tp）Fe（CN）3] （Tp =Tris（pyrazolyl）hydroborate） or [n-Bu4N][Ru（salen）（CN）2] （salen2 =N,N＇-ethylenebis（salicylideneimine）dianion） resulted in the formation of two redox-active complexes, the dinuclear heterometallic complex [（Tp）Fe（CN）3Mn（TTF-salphen）＇CH3OH] （1） and the one dimensional complex [Ru（salen）（CN）2Mn（TTF-salphen）]n （2）. Both complexes were characterized by X-ray crystallography and solid state electrochemistry, in addition to static and dynamic magnetic measurements. Antiferromagnetic couplings are found to be operative between metal ion centers bridged by cyanide in both complexes. Complex 1 exhibited field-induced SMM behavior with an energy barrier of 13.8 K. The introduction of the redox-active TTF unit into cyanidebridged complexes with interesting magnetic properties renders them promising candidates for the construction of new hybrid inorganic-organic materials.

Magnetic anisotropy in 5d transition metal-porphyrin molecules

Single molecule magnets(SMMs) with large magnetic anisotropy energy(MAE) have great potential applications in magnetic recording.Using the first-principles calculations,we investigate the MAE of 5 d transition metal-porphyrin-based SMMs by using the PBE and PBE+U with different U values,respectively.The results indicate that W-P,Re-P,Os-P,and Ir-P possess the considerably large MAE among 5 d TM-P SMMs.Furthermore,the MAE of 5 d TM-P can be facilely manipulated by tensile strain.The reduction of the absolute value of MAE for Ir-P molecule caused by tensile strain makes it easier to implement the writing operation.The decreasing of the occupation number of minority-spin channels of Ir-d_(x^(2)-y^(2)) orbital leads the MAE to decrease when the tensile strain increases.

Interaction and local magnetic moments of metal phthalocyanine and tetraphenylporphyrin molecules on noble metal surfaces

In order to understand the Kondo effect observed in molecular systems, first-principles calculations have been widely used to predict the ground state properties of molecules on metal substrates. In this work, the interaction and the local magnetic moments of magnetic molecules （3d-metal phthalocyanine and tetraphenylporphyrin molecules） on noble metal surfaces are investigated based on the density functional theory. The calculation results show that the dz2 orbital of the transition metal atom of the molecule plays a dominant role in the molecule-surface interaction and the adsorption energy exhibits a simple declining trend as the adsorption distance increases. In addition, the Au（111） surface generally has a weak interaction with the adsorbed molecule compared with the Cu（ll 1） surface and thus serves as a better candidate substrate for studying the Kondo effect. The relation between the local magnetic moment and the Coulomb interaction U is examined by carrying out the GGA＋U calculation according to Dudarev＇s scheme. We find that the Coulomb interaction is essential for estimating the local magnetic moment in molecule-surface systems, and we suggest that the reference values of parameter U are 2 eV for Fe and 2-3 eV for Co.

Dephasing of quantum tunnelling in molecular nanomagnets

Dephasing mechanism of quantum tunnelling in molecular magnets has been studied by means of the spin-coherentstate path integral in a mean field approximation. It is found that the fluctuating uncompensated transverse field from the dipolar-dipolar interaction between molecular magnets contributes a random phase to the quantum interference phase. The resulting transition rate is determined by the average tunnel splitting over the random phase. Such a dephasing process leads to the suppression of quenching due to the quantum phase interference, and to the steps due to odd resonances in hysteresis loop survived, which is in good agreement with experimental observations in molecular nanomagnets Fes and Mn12.

Spin Parity Effect on Magnetic Relaxation by Quantum Tunneling in Nanomagnets

Spin parity effect on magnetic relaxation by quantum tunneling in the biaxial spin model is studied by taking into account the transverse local stray field. It is shown that the square root time dependence in the even resonance occurs in the presence of a distribution of transverse anisotropic parameters, while the odd resonance always shows exponential relaxation. Magnetic relaxation under a sweeping field is also studied. The variation of the relaxation curve with the increasing distribution width of the local stray field for even resonance is qualitatively different from that of the odd resonance. The theoretical result on even resonance is in agreement with experimental results on Fe8 system, while the prediction for odd resonance awaits the experimental verification.

Resonant tunnelling of the magnetization in molecular crystal of [（Mn1-xCrx）12O12 （CH3COO）16（H2O）4]·2CH3COOH·4H2O（x=0,0.03,0.04,0.05）

The quantum tunnelling of magnetization （QTM） in single crystals of the single molecule magnet （Mn1-xCrx）12- Ac （x=0, 0.03, 0.04, 0.05） has been investigated. In comparison with its parent Mnl2-Ac, a greater rate of magnetization relaxation and a lower effective potential-energy barrier have been observed in Cr-doping samples. This modulation of QTM due to the Cr-doping could be attributed to the small change of Sz due to the smaller spin of Cr itself and additional intrinsic but distributed transverse and longitudinal anisotropy raised by a subtle change of the local environment in the magnetic Mn12 core.

Boosting the proton conduction in a magnetic dysprosium-organic framework by introducing conjugate NH_(4)^(+)-NH_(3)pairs

Metal-organic frameworks(MOFs)with inherent porosity and suspended acidic groups are promising proton conducting materials in water or aqua-ammonia media.Herein we report a new lanthanide phosphonate,namely,Dy_(2)(amp_(2)H_(2))_(2)(mal)(H_(2)O)_(2)·5H2O(MDAF-6).It possesses a 3D open-framework structure,and shows a high NH_(3)adsorption capacity of 142.4 cm^(3)/g at P/P0=0.98 at 298 K due to acid-base interaction.Interestingly,the proton conductivity of MDAF-6-NH3 is enhanced by five orders of magnitude compared to MDAF-6 after 8.5 h exposure in saturated NH_(3)-H_(2)O vapor,indicating the importance of coexistent conjugate acid-base pairs of H_(3)O+-H_(2)O and NH_(4)^(+)-NH_(3)in promoting proton conduction.Magnetic studies of MDAF-6 revealed slow magnetization relaxation under zero dc field,characteristic of singlemolecule magnet behavior.This work provides not only a new multifunctional MOF material,but also a new strategy to improve proton conduction in aqua-ammonia medium.

Thermo-induced structural transformation with synergistic optical and magnetic changes in ytterbium and erbium complexes

Dinuclear ytterbium and erbium based bifunction complexes Ln_(2) L_(2)(depma_(2))Cl_(2)(1-Ln,Ln=Yb and Er,H_(2) L=N~1,N~3-bis(salicylideneimino)diethylenetriamine,depma_(2)=dimerized 9-diethyl-phosphonomethylanthracene)are reported.They undergo thermo-induced consecutive phase transitions,first the dissociation of depma_(2) ligand forming LnL(depma)Cl(2-Ln)and then the release of chloroethane forming LnL(epma)(3-Ln,epma=9-ethylphosphonomethylanthrancene).The structural transformations are accompanied with synergetic switch of the luminescence in visible and NIR regions and also magnetic dynamics.

Surface geometry and magnetism of Eu@C_(60) monolayer on Ag(111)

The surface geometry, electronic structure, and magnetism of Eu@C60 monolayer absorbed on Ag(111) have been investigated within the framework of density functional theory. The Eu@C60 monolayer has been constructed on Ag(111) substrate by one of the hexagon faces of C60 downward and its mirror plane face parallel to Ag(111). The Eu@C60 monolayer induces a recon- struction of the Ag(111) substrate and the perpendicular distance between the Eu@C60 and Ag(111) surface is 2.06 A, being shorter than that between C60 and Ag(lll) surface by 0.05A. There is no chemical bond formed between the Eu@C60 and Ag(111), and only 0.55e transferred from Ag(111) to Eu@C60. A large magnetic moment about 6.80/μB per unit cell is found for Eu@C60/Ag(111) system.

Synthesis and applications of lanthanoid complexes of pentadentate and hexadentate N_(5) and N_(6) macrocycles:A review

In this paper,the lanthanoid complexes of N_(5) and N_(6) macrocycle ligands,without pendant arms or additional heteroatoms,are surveyed.This review covers the period from 2015 to the current date,since in 2014 Schiff base macrocyclic ligands incorporating the pyridine moiety,and their complexes,were revised,and in 2015 the chemistry of pentaaza macrocycle ligands with rare earth metals was also summarized.Porphyrin and phthalocyanine ligands are not included in this review,which primarily focuses on complexes with Schiff bases and amines without pendant arms or any additional donor other than nitrogen.The synthetic methods,structural characterization,based on single X-ray crystal data,and properties of the lanthanoid complexes,with special attention to magneto-structural correlations,are presented herein.