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The magnetic state of an antiferromagnetic (AFM) insulator can be read and manipulated in spintronics devices using bilayers of an AFM and a conducting layer, making it useful for spintronics devices. To date, research has focused on single crystals of AFMs, which enables the study of properties related to different crystallographic surfaces. However, combining single-crystal AFMs in spintronics devices may be problematic due to substrate selectivity and deposition conditions. In this work, we study the properties of polycrystalline Fe2O3 coupled with Pt as the conducting layer, asking how the magnetoresistive behavior differs in polycrystalline AFMs. We report on the angle dependent magnetoresistance and transverse magnetoresistance properties as a function of temperature and magnetic fields, comparing Fe2O3/Pt and Fe2O3/Cu/Pt thin films, in addition to magnetometry and structural characterization. The magnetoresistance signals do not depend on the thickness or volume behavior of the Fe2O3 layer, but rather the Fe2O3/Pt interface. Angle dependent magnetoresistance measurements show ferromagnetic-like behavior but with a non-standard effect of field, while transverse measurements show a sign change with temperature. This differs from effects reported for single-crystal Fe2O3 based bilayers. Interestingly, using transverse field measurements, we find that at low temperatures, the Fe2O3/Pt interface spins develop a glass-like relaxation of the magnetic signal, which undergoes freezing as the sample is further cooled. [ABSTRACT FROM AUTHOR]

The Mn3AgN-based manganese nitrides have attracted continuous attention due to the interesting functional properties, which is closely correlated with the magnetic evolution coupling with structural and electrical order. However, the attention on the fundamental magnetic behavior of the Mn3AgN matrix is still insufficient up to now. Here, the magnetic properties of Mn3AgN have been investigated by comprehensive magnetic measurements including dc magnetization, ac susceptibility, and magnetic relaxation. The results show that Mn3AgN undergoes two magnetic transitions with decreasing temperature: the transition from paramagnetic to antiferromagnetic (AFM) state at ∼285 K and from AFM to spin-glass-like (SGL) state at ∼110 K. The SGL state is essentially a mixed magnetic state of weak short-range ferromagnetic order and spin glass, and its appearance should be related to the AFM configuration of Γ4g with ferromagnetic component. The unique low-temperature magnetic structure of Mn3AgN makes it exhibit interesting low temperatures magnetic behavior, such as the magnetic irreversibility phenomenon, magnetic relaxation behavior, and so on. [ABSTRACT FROM AUTHOR]

Fermi's golden rule (FGR) offers an empirical framework for understanding the dynamics of spin–lattice relaxation in magnetic molecules, encompassing mechanisms like direct (one-phonon) and Raman (two-phonon) processes. These principles effectively model experimental longitudinal relaxation rates, denoted as T 1 − 1 . However, under scenarios of increased coupling strength and nonlinear spin–lattice interactions, FGR's applicability may diminish. This paper numerically evaluates the exact spin–lattice relaxation rate kernels, employing the extended dissipaton equation of motion formalism. Our calculations reveal that when quadratic spin–lattice coupling is considered, the rate kernels exhibit a free induction decay-like feature, and the damping rates depend on the interaction strength. We observe that the temperature dependence predicted by FGR significantly deviates from the exact results since FGR ignores the higher order effects and the non-Markovian nature of spin–lattice relaxation. Our methods can be easily extended to study other systems with nonlinear spin–lattice interactions and provide valuable insights into the temperature dependence of T1 in molecular qubits when the coupling is strong. [ABSTRACT FROM AUTHOR]

The study of electrolytic solutions is of relevance in many research fields, ranging from biophysics, materials, and colloid science to catalysis and electrochemistry. The dependence of solution dynamics on the nature of electrolytes and their concentrations has been the subject of many experimental and computational studies, yet it remains challenging to obtain a full understanding of the factors that govern solution behavior. Here, we provide additional insights into the behavior of aqueous solutions of alkali chlorides by combining 17O relaxation data with diffusion and viscosity data and contrast their behavior with 1H nuclear magnetic resonance relaxation data. The main findings are that 17O relaxation correlates well with viscosity data but not with diffusion data, while 1H relaxation correlates with neither. Certain ionic trends match known ion-specific series behavior, especially at high concentrations. Notably, we also examine the ranges of the interactions and conclude that the majority of the effects are tied to local water reorientation dynamics. [ABSTRACT FROM AUTHOR]

We investigated the field-dependent Néel relaxation time of magnetic nanoparticles (MNPs) in an AC excitation field. Specifically, a fundamental component of the magnetization for immobilized MNPs was studied by numerical simulation while changing the frequency f and amplitude Hac of the field. From the simulation results, we clarified the Hac dependence of the effective Néel relaxation time τN,e and obtained an empirical expression for τN,e(Hac) for the first time. The expression was obtained for the cases when the angle of the easy axis of magnetization in MNPs is fixed and randomly distributed. Using the Hac dependencies of τN,e and the previously reported Brownian relaxation time τB,e, we showed that the behavior of suspended MNPs changes from Brownian-dominant to Néel-dominant when Hac increases, even when the MNP parameters are fixed, and we obtained an expression for the boundary field between them. Furthermore, we classified several types of responses for the suspended MNPs in the AC field using the magnitude relationship among τN,e(Hac), τB,e(Hac), and 1/(2πf). Finally, we experimentally verified the classification, and reasonable agreement was observed between the experiment and analysis. The results are useful for determining suitable MNP parameters and excitation conditions for various biomedical applications. [ABSTRACT FROM AUTHOR]

The study and modeling of water exchange in complex media using different applications of diffusion and relaxation magnetic resonance (MR) have been of interest in recent years. Most models attempt to describe this process using a first order kinetics expression, which is appropriate to describe chemical exchange; however, it may not be suitable to describe diffusion-driven exchange since it has no direct relationship to diffusion dynamics of water molecules. In this paper, these limitations are addressed through a more general exchange expression that does consider such important properties. This exchange fraction expression features a multi-exponential recovery at short times and a mono-exponential decay at long times, both of which are not captured by the first order kinetics expression. Furthermore, simplified exchange expressions containing partial information of the analyzed system's diffusion and relaxation processes and geometry are proposed, which can potentially be employed in already established estimation protocols. Finally, exchange fractions estimated from simulated MR data and derived here were compared, showing qualitative similarities but quantitative differences, suggesting that the features of the derived exchange fraction in this paper can be partially recovered by employing an existing estimation framework. [ABSTRACT FROM AUTHOR]

Three dinuclear dysprosium complexes 1–3 with structural formulas [Dy2(bptz)(tta)6]·2CH2Cl2 (1), [Dy2(H2bmtz)(tta)6] (2) and [Dy2(H2bmtz)(hfac)6(H2O)2] (3) (bptz = 3,6-di(2-pyridyl)-1,2,4,5-tetrazine, H2bmtz = 3,6-di(2-pyrimidyl)-1,4-dihydro-1,2,4,5-tetrazine, tta = 2-thenoyltrifluoroacetonate, hfac = hexafluoroacetylacetonate) were synthesized by the use of two tetrazine derivative ligands containing six and eight nitrogen atoms in combination with β-diketonate co-ligands, which are a good research platform to study the synergistic influence of the local coordination environment and magnetic interaction on magnetic relaxation. Complexes 1 and 2 possess the same peripheral co-ligands and nearly the same coordination environment (approaching an ideal triangular dodecahedron), but different multi-nitrogen bridges involving N6 (bptz) and N8 (H2bmtz) tetrazine derivatives. The structural difference leads to distinct magnetic relaxation properties with a hysteresis temperature of 2.5 K and 5.5 K at a rate of 200 Oe s−1 in 1 and 2, respectively, which is most likely due to the different magnetic coupling transmitted by H2bmtz and bptz in the direction close to the vertical magneto axis. Combined with a suitable local coordination environment, the energy barrier of complex 2 bridged by H2bmtz can reach three times that of complex 3. Considering the local ligand field, the important influence of this multi-nitrogen bridge transmitting magnetic coupling on the SMM properties is demonstrated with the aid of ab initio calculations. Also of note is that complexes 2 and 3 are the first reported lanthanide SMMs constructed from dihydro-tetrazine. [ABSTRACT FROM AUTHOR]

ABSTRACT Two Co (II) compounds [Co (abs)2]·2H2O (1) and [Co (pabs)2] (2) (Habs = N‐(pyridine‐2′‐yl methylene)‐2‐aminobenzene sulfonic acid, Hpabs = N‐[(pyridine‐2′‐yl)(phenyl)methylene]‐2‐aminobenzene sulfonic acid) were synthesized by the introduction of sulfonate ligands with different substitutions. Both Co (II) ions are located in a trigonal prism coordination environment with different coordination distortions. Static magnetic studies and theoretical calculations found that easy‐axis magnetic anisotropy is present in both complexes. The contributions of the negative D values are principally derived from the first quartet excited state. Dynamic magnetic investigations uncovered that both compounds have field‐induced single‐ion magnet (SIM) behavior and their magnetic relaxations mainly realize through Raman and direct pathways. [ABSTRACT FROM AUTHOR]

Based on a β-diketonate ligand, a mononuclear Dy(III) complex, [Dy(dmpd)3(bpy)] (1) (dmpd = 4,4-dimethyl-1-phenylpentane-1,3-dione, bpy = 2,2′-dipyridyl), of [DyN2O6] type has been synthesized with a capping nitrogen-containing coligand. Then, a dual capping coligand 2,2′-bipyrimidine (bmp) is introduced to be a bridge to link two β-diketonate-Dy(III) motifs, leading to a new dinuclear Dy(III) complex, [Dy2(dmpd)6(bmp)] (2). Dy(III) centers in both complexes feature an N2O6 octacoordinated environment with an approximate square-antiprism geometry (D4d). Without a dc field, the SMM behaviour is absent in complex 1, but can be clearly observed in dinuclear 2 with a Ueff of 87.29 K. The significantly improved magnetism arising in 2 is mainly due to the modulation of the coordination environment around the Dy(III) ions and the superexchange magnetic interactions inside the dinuclear units, thus allowing for the effective inhibition of the quantum tunneling of magnetization at low temperatures and promotion of the uniaxial magnetic anisotropy. For 1, a diamagnetic Y(III) analogue [Y(dmpd)3(bpy)] (3) and diluted sample 1@Y were constructed to further perform the dilution experiment, coupled with theoretical calculations further supporting that the synergetic contributions of intermolecular dipole–dipole interactions, intramolecular coupling and uniaxial magnetic anisotropy cause the enhancement of dynamic magnetic relaxation. [ABSTRACT FROM AUTHOR]

Over the years, polynuclear cyclic or torus complexes have attracted increasing interest due to their unique metal topologies and properties. However, the isolation of polynuclear cyclic organometallic complexes is extremely challenging due to their inherent reactivity, which stems from the labile and reactive metal‐carbon bonds. In this study, the pyrazine ligand undergoes a radical‐radical cross‐coupling reaction leading to the formation of a decanuclear [(Cp*)20Dy10(L1)10] ⋅ 12(C7H8) (1; where L1 = anion of 2‐prop‐2‐enyl‐2H‐pyrazine; Cp* = pentamethylcyclopentadienyl) complex, where all DyIII metal centres are bridged by the anionic L1 ligand. Amongst the family of polynuclear Ln organometallic complexes bearing CpR2Lnx units (CpR = substituted cyclopentadienyl), 1 features the highest nuclearity obtained to date. In‐depth computational studies were conducted to elucidate the proposed reaction mechanism and formation of L1, while probing of the magnetic properties of 1, revealed slow magnetic relaxation upon application of a static dc field. [ABSTRACT FROM AUTHOR]

Magnetic semiconductors, with integrated properties of ferromagnets and semiconductors, are significant for developing next‐generation spintronic devices. Herein two atomically precise clusters of dysprosium(III) tellurides, formulated respectively as [Na2(15‐crown‐5)3(py)2][(η5‐Cp*Dy)5(Te)6](py)4 (Dy5Te6, Cp*=pentamethylcyclopentadienyl; py=pyridine) and [K(2,2,2‐cryptand)]2[(η5‐Cp*Dy)6(Te3)(Te2)2(Te)3] (Dy6Te10), are reported. Crystallographic studies revealed the presence of multifarious tellurido ligands within the polyhedral cluster cores. Spectroscopic and magnetic studies showed that both clusters are single‐molecule magnets exhibiting slow magnetic relaxation behaviors at low temperatures and semiconductors with low optical band gaps comparable to benchmark semiconductors. These clusters represent probably the first lanthanide‐based molecular magnetic semiconductors. [ABSTRACT FROM AUTHOR]

Dinuclear Ni(II)/Ce(III) complexes, namely [Ni(o-van-dap)Ce(H2O)(NO3)3] (1) and [Ni(H2O)2(o-van-dmdap)Ce(NO3)3] (2), were synthesized and chemically and spectroscopically characterized. Single crystal X-ray analyses revealed that in both 1 and 2 bicompartmental Schiff base-type ligands (o-van-dap)2− and (o-van-dmdap)2− are present, with neighbouring cis-N2O2 and O4 donor sets. The smaller N2O2 cavity is occupied by the Ni(II) ions while the larger O4 cavity contains a Ce(III) ion; both metal ions are linked via a pair of monoatomic O-bridges with the O atoms provided by deprotonated hydroxyl groups. In complex 1 the bridging unit within the Schiff base-type ligand is formed from two carbon atoms; consequently the central Ni(II) atom has a square-planar geometry, and is thus diamagnetic. In complex 2 the bridging unit within the structure of the ligand is composed of three carbon atoms yielding a larger cavity accommodating a paramagnetic, hexacoordinated Ni(II) atom, whose coordination sphere is completed by two axial aqua ligands. The Ce(III) atoms in both 1 and 2 are additionally coordinated by three chelating nitrato co-ligands resulting in coordination number 10 in 2, while another aqua ligand increases the coordination number of the Ce(III) atom in 1 to 11. Variable temperature dc magnetic studies of both 1 and 2 (2–300 K) corroborate the diamagnetism of the Ni(II) atom (S = 0) in 1 and paramagnetism of the Ni(II) atom (S = 1) in 2. The ac magnetic studies showed that both complexes 1 and 2 exhibit field induced slow magnetic relaxation. The obtained values of the energy barriers are Δ/kB = 24.1 K with τ0 = 6.96 × 10−8 s for 1, and Δ/kB = 9.88 K with τ0 = 5.36 × 10−7 s for 2. One-atomic elongation of the bridging unit in the bicompartmental ligand induces change of the magnetic character of the Ni(II) central atoms from S = 0 in 1 to S = 1 in 2, and this change leads to significant differences in the values of the respective Δ/kB parameters. Theoretical ab initio calculations for complexes 1 and 2 were performed to investigate their magnetic properties in detail. [ABSTRACT FROM AUTHOR]

The synthesis, structures, adsorption, and magnetic properties of two two-dimensional (2D) coordination polymers, [M(btca)1/2(bpe)1/2(H2O)2]n (M = Ni2+ (1) and Co2+ (2); H4btca = 1,2,4,5-benzenetetracarboxylic acid; bpe = 1,2-di(4-pyridyl)ethane) constructed by mixed bipyridyl–tetracarboxylate ligands were reported. Single-crystal X-ray diffraction studies reveal the 3D hydrogen-bonded networks sustained by O–H⋯O H bonds between the 2D layers. The 2D structure topology of the compounds is a new {4.6·2}2{4·2.6·2.8·2} bex topology while the 3D framework is different because of the distinct H bond interactions. Both compounds exhibit high thermal stability above 150 °C. N2 adsorption measurements reveal that both compounds are non-porous structures, while compound 1 exhibits CO2 adsorption, possibly due to structural expansion after CO2 accommodation. Magnetic investigations indicated that framework 2 exhibits field-induced slow magnetic relaxation due to the large magnetic anisotropy of Co2+ ions (zero-field splitting parameter D = 42.1 cm−1), while framework 1 shows simple paramagnetism with a small D of −11.3 cm−1. This work not only provides two new coordination polymers but also a potential bipyridyl–tetracarboxylate approach for the design and construction of single-ion magnet (SIM) frameworks. [ABSTRACT FROM AUTHOR]

Coordination compounds with slow magnetic relaxation are of great interest due to their magnetic bistability. Herein, three cobalt(II) coordination polymers, formulated as {[Co2(btca)(bpym)]·4H2O}n (1) and {[Co2(btca)(bpym)]·2DMF·2H2O}n (2), {[Co2(H2btca)2(bpym)]}n (3) (H4btca = 1,2,4,5-benzenetetracarboxylic acid; bpym = 2,2′-bipyrimidine), were solvothermally synthesized and magnetically characterized. Single-crystal structural analyses reveal that compounds 1 and 2 are Co2+ dimer-based one-dimensional (1D) and 2D coordination polymers, respectively, while compound 3 is a Co2+ chain-based 2D coordination polymer with a new topology. The Co2+ dimers and chains in these compounds are well magnetically isolated due to the bulk tetracarboxylic linker. Magnetic studies reveal that antiferromagnetic interactions exist between the Co2+ ions bridged by the bpym ligand. For 1, no relaxation behavior can be detected, suggesting the paramagnetic behavior of 1. Interestingly, alternating current (AC) magnetic measurements observed slow magnetic relaxation under a 1000 Oe field for 2 and 3. These results provide not only three cobalt(II) coordination polymers with varying topology and magnetic behaviors but also a pyrimidine–tetracarboxylic ligand platform for designing new slow magnetic relaxing coordination polymers. [ABSTRACT FROM AUTHOR]

Background and Aims Intravenous iron therapies contain iron–carbohydrate complexes, designed to ensure iron becomes bioavailable via the intermediary of spleen and liver reticuloendothelial macrophages. How other tissues obtain and handle this iron remains unknown. This study addresses this question in the context of the heart. Methods A prospective observational study was conducted in 12 patients receiving ferric carboxymaltose (FCM) for iron deficiency. Myocardial, spleen, and liver magnetic resonance relaxation times and plasma iron markers were collected longitudinally. To examine the handling of iron taken up by the myocardium, intracellular labile iron pool (LIP) was imaged in FCM-treated mice and cells. Results In patients, myocardial relaxation time T1 dropped maximally 3 h post-FCM, remaining low 42 days later, while splenic T1 dropped maximally at 14 days, recovering by 42 days. In plasma, non-transferrin-bound iron (NTBI) peaked at 3 h, while ferritin peaked at 14 days. Changes in liver T1 diverged among patients. In mice, myocardial LIP rose 1 h and remained elevated 42 days after FCM. In cardiomyocytes, FCM exposure raised LIP rapidly. This was prevented by inhibitors of NTBI transporters T-type and L-type calcium channels and divalent metal transporter 1. Conclusions Intravenous iron therapy with FCM delivers iron to the myocardium rapidly through NTBI transporters, independently of reticuloendothelial macrophages. This iron remains labile for weeks, reflecting the myocardium's limited iron storage capacity. These findings challenge current notions of how the heart obtains iron from these therapies and highlight the potential for long-term dosing to cause cumulative iron build-up in the heart. [ABSTRACT FROM AUTHOR]

The introduction of the cerium(III) analogue (1‐Ce, Ln = Ce) of (tert‐butoxido)chloridopentakis(tetrahydrofuran)lanthanide(III) tetraphenylborate tetrahydrofuran disolvate, [Ln{OC(CH3)3}Cl(C4H8O)5][B(C6H5)4]·2C4H8O or [Ln(OtBu)Cl(THF)5](BPh4)·2THF (1‐Ln) has been achieved with a structural comparison between the existing solid‐state structures of other rare earth analogues and the title compound at 100 and 180 K. The cation in 1‐Ce is targeted as the cerium(III) ion possesses the criteria to exhibit slow magnetic relaxation in axial point‐charge crystal fields, akin to the dysprosium(III) ion in 1‐Dy. AC magnetic susceptibility experiments reveal no such behaviour for 1‐Ce, putting the viability of cerium‐based SMMs into question. [ABSTRACT FROM AUTHOR]

This study explores the mechanical and magnetic properties of magnetorheological elastomers (MREs) based on chloroprene rubber, enhanced with carbonyl iron powder (CIP) as the primary filler. Carbon black serves as the primary reinforcing filler, with multi‐walled carbon nanotubes (CNTs) used as a secondary filler to strengthen the rubber matrix. The primary objective of this research is to examine the effects of the mixture of iron powder with reinforcing fillers and the interaction of these fillers with the rubber matrix on the mechanical and magnetomechanical performance of MREs. CNTs, tubular nanoscale carbon molecules, significantly enhance the tensile strength and fatigue resistance when combined with the MRE matrix. During mixing, CNTs form a network structure within the MRE matrix, promoting the dissipation of accumulated heat and reducing thermal fatigue loss. The addition of 20 parts of CNTs to the CR matrix significantly improved the tensile mechanical properties, with the 100% set elongation stress increasing by up to 260% and the magnetic responsiveness increasing by 30.6%. The addition of 10 parts of carboxylated CNTs most notably enhanced the magnetorheological effect, increasing the magnetic stress relaxation rate by 78%. These enhanced properties enable MREs to provide better vibration control and comfort in automotive suspension systems, improve energy absorption and damping effects in industrial damping systems, and enhance durability and sealing performance in sealant applications. Highlights: Carbonyl iron powder, carbon black, and carbon nanotubes (CNTs) were used as fillers to strengthen the chloroprene (CR) matrix magnetorheological elastomers (MREs).CNTs formed a network structure, promoting the dissipation of accumulated heat and reducing thermal fatigue loss.The tensile mechanical property of MRE with 20 parts of CNTs has been significantly improved, with an increasing magnetic responsiveness of 30.6%.Magnetorheological effect of MRE with 10 parts of CNTs has notably enhanced, with the magnetic stress relaxation rate of 78%. [ABSTRACT FROM AUTHOR]

The longitudinal and transverse nuclear magnetic resonance relaxivity dispersion (NMRD) of 1H in water induced by the paramagnetic relaxation enhancement (PRE) of dissolved lanthanide ions (Ln3+) can become very strong. Longitudinal and transverse 1H NMRD for Gd3+, Dy3+, Er3+ and Ho3+ were measured from 20 MHz/0.47 T to 1382 MHz/32.5 T, which extended previous studies by a factor of more than two in the frequency range. For the NMRD above 800 MHz, we used a resistive magnet, which exhibits reduced field homogeneity and stability in comparison to superconducting and permanent NMR magnets. These drawbacks were addressed by dedicated NMRD methods. In a comparison of NMRD measurements between 800 MHz and 950 MHz performed in both superconducting and resistive magnets, it was found that the longitudinal relaxivities were almost identical. However, the magnetic field fluctuations of the resistive magnet strongly perturbed the transverse relaxation. The longitudinal NMRDs are consistent with previous work up to 600 MHz. The transverse NMRD nearly scales with the longitudinal one with a factor close to one. The data can be interpreted within a PRE model that comprises the dipolar hyperfine interactions between the 1H and the paramagnetic ions, as well as a Curie spin contribution that is dominant at high magnetic fields for Dy3+, Er3+ and Ho3+. Our findings provide a solid methodological basis and valuable quantitative insights for future high-frequency NMRD studies, enhancing the measurement accuracy and applicability of PRE models for paramagnetic ions in aqueous solutions. [ABSTRACT FROM AUTHOR]

We report the synthesis, structures and magnetic behaviour of two isostructural dinuclear Dy3+ complexes where the metal ions of a previously reported monomeric building block are connected by a peroxide (O22−) or a pair of fluoride (2×F−) bridges. The nature of the bridge determines the distance between the metal ion dipoles leading to a dipolar coupling in the peroxido bridged compound of only ca. 70 % of that in the bis‐fluorido bridged dimer. The sign of the overall coupling between the metals is antiferromagnetic for the peroxido bridged compound and ferromagnetic for the bis‐fluorido bridged complex. This in turn influences the magnetisation dynamics. We compare the relaxation characteristics of the dimers with those of the previously reported monomeric building block. The relaxation dynamics for the bis‐fluorido system are very fast. On the other hand, comparing the properties of the monomer, the peroxido bridged sample and the corresponding Y‐doped sample show that the relaxation properties via a Raman process have very similar parameters. We show that a second dysprosium is important for either tuning or detuning the Single Molecule Magnet (SMM) properties of a system. [ABSTRACT FROM AUTHOR]

Precise control at the colloidal scale is one of the most promising bottom-up approaches to fabricating new materials and devices with tunable and precisely engineered properties. Magnetically driven colloidal assembly offers great versatility because of the ability to externally tune particle-particle interactions and to construct a host of particle arrangements. However, despite previous efforts to probe the parameter space, global orientational control in conjunction with two-dimensional microstructural control has remained out of reach. Furthermore, the magnetic relaxation time of superparamagnetic beads has been largely overlooked despite being a key feature of the magnetic response. Here, we take advantage of the magnetic relaxation time of superparamagnetic beads in an alternating rotating magnetic field and show how harnessing this feature facilitates the formation of oriented clusters. The orientation of these clusters can be controlled by field parameters. Using experiments, simulations, and theory, we probe a two-particle system (dimer) under this alternating rotating magnetic field and use its dynamics to provide insights into the collective response that forms clusters. We find that the type of field has significant implications for the dipolar interactions between the colloids because of the nonnegligible magnetic relaxation. Moreover, we find that the competing time scales of the magnetic relaxation and the alternating field generate an anisotropic interaction potential that drives cluster alignment. By exploiting the magnetic relaxation time of magnetic systems, we can tailor new types of interparticle interactions, thereby expanding the capabilities of colloidal assembly in engineering unique materials and devices. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Two families of cyclopentadienyl (Cp)/carboranyl heteroleptic sandwiched organolanthanide complexes, namely [Ln{η5:σ‐Me2C(C5H4)(C2B10H10)}2][Li(DME)3] (1Ln, Ln = Tb, Dy, Ho, Er) and [2‐THF‐2'‐(μ2‐Cl)Li(THF)3‐2,2'‐Ln(nido‐1,7‐C2B9H11)Cp*] (2Dy), were synthesized. Family of 1Ln has been proposed based on the mixing‐ligands idea by linking Cp and nido‐dicarborllide. However, the carborane cage of [Me2C(C5H4)(C2B10H10)]2− deprotons and forms a mono‐C− anion rather than deboron to form dicarborllide dianion. Hence, the family of 1Ln features a dysprosocenium skeleton with extra two coordination of C− anions of carborllides. Such coordination geometry is more like a tetrahedron if abstracting the centroids of two coordinated Cp rings. In this cubic‐type geometry, no significant magnetic axiality is presented; only 1Dy and 1Tb show field‐induced slow magnetic relaxation behavior below 10 K. Inspired by 1Ln, the free pentamethylcyclopentadienyl (Cp*−) and nido‐dicarborllide ligands are used to sandwich central Dy3+ ion, achieving heteroleptic complex 2Dy. The bending angle by linking the centroid of Cp*−, Dy3+ and C2B32− in 2Dy is increased to 132.8(1)°. As such, the effective energy barrier for magnetic reversal (Ueff) and magnetic blocking temperature TB (ZFC) are both increased (Ueff = 616(10) K; TB = 6 K). The effort of further enhancing Ueff and TB in such heteroleptic organolanthanide sandwiches should rely on keeping increasing the ligand axiality. [ABSTRACT FROM AUTHOR]

5-(4-pyridyl) phenyl substituted functionalized nitronyl nitroxide biradical ligand holds MnII ions and TbIII / HoIII ions together to yield 3d-4f-biradical heterospin clusters, namely, [Ln2 Mn2 (hfac)10 (NITPhPybis)2] [Ln = Tb 1, Ho 2], wherein, two NITPhPybis radicals ligate two MnII ions via two NO groups and two nitrogen-atoms from pyridine rings. At the same time, each NITPhPybis encapsulates one LnIII ion through chelating mode with adjacent NO groups, generating an annular centrosymmetric heterometallic tetranuclear system. In addition, the direct current and alternating current magnetic properties and luminescent behavior were systematically studied. Magnetodynamic studies uncover that the cluster 1-TbMn exhibits slow magnetic relaxation. The fluorescence of two polynuclear clusters show the characteristic fluorescence of TbIII or HoIII ions. [ABSTRACT FROM AUTHOR]

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. The aim of the study was to enquire to which extend 1H spin-lattice nuclear magnetic resonance (NMR) relaxometry data collected over a broad range of resonance frequencies (from 10 kHz to 10 MHz) have the potential to be used for assessing quality and authenticity of different categories of cheese. The following cheeses were selected mozzarella, processed cheese, pizza cheese, pizza cheese with modified fat phase), low-fat cheese, and long ripened cheese. The cheeses from 3 different production plants and various cheese production batches were used in the study. The samples from each group were subjected to instrumental composition analysis (FoodScan analyzer type 78810, FOSS, Hillerod, Denmark), water activity assessment (Aqualab 4TEV analyzer, type S40001855) and nuclear magnetic resonance relaxation dispersion study (SMARtracer FFC relaxometer, Stelar S.r.l , Italy). The state and dynamics of water present in products as free and bound water largely determines the properties of food products, including cheeses. Nuclear magnetic resonance relaxometry studies of cheese enable to reveal relaxation features characteristic of specific categories of cheese. Consequently, the studies can be treated as a step toward exploiting NMR relaxometry for accessing quality and authenticity of cheese. It was shown that at low resonance frequencies, the lower the moisture, the larger the relaxation rate. The durability and quality of cheeses depend on the presence and condition of water, so it is necessary to find a relationship between the presence, condition and mobility of water in cheeses, to increase and improve the quality and extend the shelf life. [ABSTRACT FROM AUTHOR]

Multi‐exponential decay is prevalent in magnetic resonance spectroscopy, relaxation, and imaging. This paper describes simple MATLAB and Python functions and scripts for regularized multi‐exponential analysis methods for 1D and 2D data and example test problems and experiments. Regularized least‐squares solutions provide production‐quality outputs with robust stopping rules in ~5 and ~20 lines of code for 1D and 2D inversions, respectively. The software provides an open‐architecture simple solution for transforming exponential decay data to the distribution of their decay lifetimes. Examples from magnetic resonance relaxation of a complex fluid, a Danish North Sea crude oil, and fluid mixtures in porous materials—brine/crude oil mixture in North Sea reservoir chalk—are presented. Developed codes may be incorporated in other software or directly used by other researchers, in magnetic resonance relaxation, diffusion, and imaging or other physical phenomena that require multi‐exponential analysis. [ABSTRACT FROM AUTHOR]

The reaction of Schiff base ligand N,N′-bis(salicylidene)ethylenediamine (H2L) with [CoII2(μ-OH2)(O2CCMe3)4(HO2CCMe3)4] (CoII2-Piv) (Piv = pivalate) and Ln(NO3)3·xH2O (for 1, 3, 4x = 5; for 2, x = 6) salts in the presence of triethylamine afforded [CoIIILnIII(L)(μ-Piv)2(η1-Piv)2(η1-OHMe)2] [where Ln = Dy, for 1; Tb, for 2; Ho, for 3; and Er, for 4] complexes. The heterometallic dinuclear ensemble is built via the bridging coordination action of [L]2− and four [Piv]− ligands. Further, the Ln(III) center is coordinated by two η1-OHMe ligands. Shape analysis of all the Ln(III) centers in 1–4 reveals the existence of a distorted triangular dodecahedron geometry. Magnetic studies revealed that compound 1 shows slow magnetic relaxation under zero-field at low temperatures whereas compound 4 displays field-induced slow magnetic relaxation. This phenomenon is in agreement with the results of theoretical studies. [ABSTRACT FROM AUTHOR]

A well‐judged combination of a high axial ligand field and a bridging radical ligand in a dinuclear lanthanide complex provides a single‐molecule magnet with a higher effective energy barrier for magnetic relaxation and blocking temperature compared to its non‐radical analog due to significant magnetic exchange coupling between radical and Ln(III) ions. In this work, we report two chloranilate (CA) bridged dinuclear dysprosium complexes, [{(bbpen)Dy(μ2‐CA)Dy(bbpen)}] (1Dy) and [{(bbpen)Dy(μ2‐CA⋅)Dy(bbpen)}−{CoCp2}+] (2Dy), where 2Dy is the radical bridged Dy‐complex obtained via the chemical reduction of bridging CA moiety (H2bbpen=N,N′‐bis(2‐hydroxybenzyl)‐N,N′‐bis(2‐methylpyridyl)ethylenediamine). The presence of high electronegative phenoxide moiety enhances the axial anisotropy of pseudo‐square antiprismatic Dy(III) ions. The diffused spin of radical is efficiently coupled with anisotropic Dy(III) centres and decreases the quantum tunnelling of magnetization (QTM) in the magnetic relaxation process. The magnetic relaxation of 1Dy follows Orbach, Raman, and QTM processes whereas for 2Dy it follows Orbach and Raman Processes. Due to less involvement of the QTM relaxation process, 2Dy shows a higher thermal energy barrier (Ueff=700 K) and a high blocking temperature (6.7 K), compared to its non‐radical analog. Remarkably, the radical coupled 2Dy complex shows the highest energy barrier among the radical bridged Dy(III)‐based SMMs to date. [ABSTRACT FROM AUTHOR]

Eight complexes LnIII(tfa)3(dmpy) (Ln = Gd 1, Dy 2, tfa = 1,1,1-trifluoro-2,4-pentanedione dmpy = 4,4'- dimethyl-2,2'-bipyridyl), LnIII(tfpa)3(dmpy) (Ln = Gd 3, Dy 4, tfpa = 4,4,4-trifluoro-1-phenyl-1,3- butanedione), [LnIII(tfa)3]2(bpyd) (Ln = Gd 5, Dy 6, bpyd = 2,2'-bipyrimidine) and [LnIII(tfpa)3]2(bpyd) (Ln = Gd 7, Dy 8) were designed to investigate the influence of magnetic coupling transfer and changes in molecular geometry on the performance of single-molecule magnets (SMMs). The single-crystal X-ray diffraction results show that LnIII(tfa)3(dmpy) and LnIII(tfpa)3(dmpy) are mononuclear, while [LnIII(tfa)3]2(bpyd) and [LnIII(tfpa)3]2(bpyd) are binuclear complexes with bipyrimidine acting as bridging ligands. The LnIII ions in these complexes are octahedral structures. Direct current (dc) susceptibility data indicate that bipyrimidine can effectively transfer the magnetic exchange of two LnIII ions. The results of alternating current (AC) magnetization characterization reveal that the magnetic exchange of adjacent DyIII ions can obviously suppress the quantum tunneling effect. Therefore, complexes 2 and 4 display weak magnetic relaxation with the absence of peaks. Comparatively, complexes 6 and 8 exhibit distinct slow magnetic relaxation behaviors under the same conditions, with Ueff values of 319.38 and 173.18 K, respectively. Theoretical calculations suggest that the weak DyIII--DyIII dipole--dipole interaction in complex 6 can effectively hinder the magnetic quantum tunneling in the lowest four Kramers doublets (KDs) of DyIII fragments. Consequently, the Ueff value of complex 6 is notably higher than that of complex 8. These findings could provide insights for achieving higher energy barriers in binuclear DyIII compounds. [ABSTRACT FROM AUTHOR]

Novel heteroleptic anilate-based lanthanide MOFs (LnIII = Tb, Dy, Ho) have been obtained under hydrothermal conditions by the ancillary ligand synthetic strategy. These structurally isomorphous species contain octacoordinated LnIII ions with coordination polyhedra approaching an ideal D2d symmetry, best described by a distorted biaugmented trigonal prismatic C2v geometry. In the whole series, only the Dy-MOF exhibits SMM behaviour. [ABSTRACT FROM AUTHOR]

We present herein magneto-structural studies of three heterometallic Zn2Dy complexes: [Zn2Dy(L)2Cl2(H2O)](ClO4)·4H2O (1), [Zn2Dy(L)2Br2(H2O)](ClO4)·4H2O (2) and [Zn2Dy(L)2(OAc)I(H2O)]I3·4H2O (3), utilizing a new Schiff base ligand, N,N'-bis(3-methoxy-5-methylsalicylidene)-1,2-diaminocyclohexane (H2L). Complexes 1 and 2 exhibit remarkable magnetic relaxation behaviour with relatively high energy barriers in zero field (Ueff: 244 K for 1 and 211 K for 2) and notable hysteresis temperatures, despite the low local geometric symmetry around the central DyIII ions. The SMM performance of these complexes is further enhanced under an applied magnetic field, with Ueff increasing to 309 K for 1 and 269 K for 2, positioning them as elite members within the Zn–Dy SMM family. These findings emphasize the substantial influence of remote modulation on ZnII beyond the first coordination sphere of DyIII ions on their dynamic magnetic relaxation properties. Ab initio studies demonstrate that the relative orientation of the phenoxo-oxygen donor atoms around the DyIII ion is critical for determining the magnetic anisotropy and relaxation dynamics in these systems. Additionally, experimental and theoretical investigations reveal that the coordination of the bridging acetate towards the hard plane, combined with significant distortion from the ideal ZnO2Dy diamond core arrangement caused by the acetate ion, results in low magnetic anisotropy in complex 3, thereby leading to field-induced SMM behaviour. Overall, this study unveils the effects of co-ligands on the SMM performance in a series of linear trinuclear Zn–Dy–Zn complexes, which exhibit low local geometric symmetry around the DyIII centres. [ABSTRACT FROM AUTHOR]

A new Co(II) complex, [Co(NCS)2(L)2] (1) has been synthesized based on levamisole (L) as a new ligand. Single‐crystal X‐ray diffraction analyses confirm that the Co(II) ion is having a distorted tetrahedral coordination geometry in the complex. Notably strong intramolecular S⋅⋅⋅S and S⋅⋅⋅N interactions has been confirmed by employing Quantum Theory of Atoms in Molecules (QTAIM). These intramolecular interactions occur among the sulfur and nitrogen atoms of the levamisole ligands and also the nitrogen atoms of the thiocyanate. Direct current (dc) magnetic analyses reveal presence of zero field splitting (ZFS) and large magnetic anisotropy on Co(II). Detailed ab initio ligand field theory calculations quantitatively predicted the magnitude of ZFS. Prominent field‐induced single‐ion magnet (SIM) behavior was observed for 1 from dynamic magnetization measurements. Slow magnetic relaxation follows an Orbach mechanism with the effective energy barrier Ueff=29.6 (7) K and relaxation time τo=1.4 (4)×10−9 s. [ABSTRACT FROM AUTHOR]

Magnetic flux ropes are pivotal structures and building blocks in astrophysical and laboratory plasmas, and various equilibrium models have thus been studied in the past. However, flux ropes in general form at non-equilibrium, and their pathway from formation to relaxation is a crucial process that determines their eventual properties. Here we show that any localized current parallel to a background magnetic field will evolve into a flux rope via non-equilibrium processes. The detailed kinetic dynamics are exhaustively explained through single-particle and Vlasov analyses and verified through particle-in-cell simulations. This process is consistent with many proposed mechanisms of flux rope generation such as magnetic reconnection. A spacecraft observation of an example flux rope is also presented; by invoking the non-equilibrium process, its structure and properties can be explicated down to all six components of the temperature tensor. Flux ropes are fundamental structures that govern much of the dynamics in astrophysical and space plasmas. The authors show how out-of-equilibrium processes can form small-scale flux ropes and compare them to simulations and spacecraft observations. [ABSTRACT FROM AUTHOR]

In the atomic comagnetometer, nuclear spin relaxation is a core parameter that affects the magnetic field suppression ability and stability, and is influenced by various gradient fields. It is necessary to measure and separate the effects of different gradients on nuclear spin, which helps to effectively suppress them separately. This article proposes a periodic optical pumping method for separating and measuring polarization gradient relaxation and magnetic field gradient relaxation, considering the effects of pump light and applied magnetic field. The comprehensive influence model for pump light on transverse nuclear spin relaxation is established, and the measurement steps and parameter selection criteria for the proposed method considering signal decay characteristics are provided. Furthermore, the proportion of various gradient relaxations is quantified. This work provides an evaluation method for gradient relaxation suppression, supporting the improvement of the measurement sensitivity and stability of the atomic comagnetometer. [ABSTRACT FROM AUTHOR]

DyPc2 and DyPc2•CH2Cl2 were prepared using the solvent thermal method. The x-ray diffractometer and the Fourier transform infrared spectrometer were used to explore the structure changes between DyPc2 and DyPc2•CH2Cl2. The results clearly demonstrate that the CH2Cl2 molecule can alter the crystal structures and, thus, change the molecular stacking structures of DyPc2 without destroying molecular integrity. Geometry optimization further proved that DyPc2 belongs to the space group P212121, while DyPc2•CH2Cl2 crystallizes in the space group Pnma. It is clearly demonstrated that the different molecular environment affects the structure of a single DyPc2 molecule to some extent, such as the twist angles of two Pc rings and the Pc−Dy−Pc angles. The molar magnetic susceptibility and hysteresis loops for DyPc2 and DyPc2•CH2Cl2 were also measured and compared. The negative Weiss constants were obtained by the Curie−Weiss law fitting above 50 K. The hysteresis loop for DyPc2•CH2Cl2 is wider than that of DyPc2, implying that the magnetic relaxation of DyPc2 slowed down, while quantum tunneling of the magnetization is prevented efficiently after absorbing CH2Cl2 molecules. This work clarifies the correlation between the molecular environment and magnetism of single-molecule magnets, which is helpful for their design guideline and future applications. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Many sandwich‐type lanthanide complexes show extremely high energy barriers (Ueff) for the reversal of magnetization and high blocking temperatures, being the star molecules in the research area of single‐molecule magnets. Herein, the preparation, structural determination, and magnetic property studies of two ansa‐bridged Er‐COT (COT = cyclooctatetraenyl dianion) complexes [KDME2][Er((η8‐COT‐SiMe2)2O)] (1) and [KDME2][Er((η8‐COT‐SiiPr2)2O)]K[Er((η8‐COT‐SiiPr2)2O)] (2) were reported. The Er(III) ions in both complexes are sandwiched by two COT rings which are ansa‐bridged by a [Si‐O‐Si] group. Magnetic studies reveal both complexes display slow magnetic relaxations with comparable energy barriers (228(5) K for 1, and 196(4) K for 2) and blocking temperatures (10.5 K for both complexes). The difference in the relaxation times (τ) for the two complexes was studied in details: different molecular vibrations induced by the substituents are the main reason for τ for 1 being about 10 times longer than for 2 at the same temperature above 10 K, while the quantum tunnelling of magnetization relaxation time (τQTM) for 2 is about 10 times longer than for 1 below 8 K, probably owing to the different dipolar interactions. Further rearrangement of molecular network with such ansa‐bridged SMMs is promising to design molecular magnetic materials with enhanced properties or new properties. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Many sandwich‐type lanthanide complexes show extremely high energy barriers (Ueff) for the reversal of magnetization and high blocking temperatures, being the star molecules in the research area of single‐molecule magnets. Herein, the preparation, structural determination, and magnetic property studies of two ansa‐bridged Er‐COT (COT = cyclooctatetraenyl dianion) complexes [KDME2][Er((η8‐COT‐SiMe2)2O)] (1) and [KDME2][Er((η8‐COT‐SiiPr2)2O)]K[Er((η8‐COT‐SiiPr2)2O)] (2) were reported. The Er(III) ions in both complexes are sandwiched by two COT rings which are ansa‐bridged by a [Si‐O‐Si] group. Magnetic studies reveal both complexes display slow magnetic relaxations with comparable energy barriers (228(5) K for 1, and 196(4) K for 2) and blocking temperatures (10.5 K for both complexes). The difference in the relaxation times (τ) for the two complexes was studied in details: different molecular vibrations induced by the substituents are the main reason for τ for 1 being about 10 times longer than for 2 at the same temperature above 10 K, while the quantum tunnelling of magnetization relaxation time (τQTM) for 2 is about 10 times longer than for 1 below 8 K, probably owing to the different dipolar interactions. Further rearrangement of molecular network with such ansa‐bridged SMMs is promising to design molecular magnetic materials with enhanced properties or new properties. [ABSTRACT FROM AUTHOR]

Detailed state-of-the-art ab initio and density functional theory (DFT) calculations have been undertaken to understand both Single-Molecule Magnetic (SMM) and Single-Molecule Toroic (SMT) behaviors of fascinating 3d–4f {M3Ln3} triangular complexes having the molecular formula [M II3 Ln III3 (O2)L3(PyCO2)3](OH)2(ClO4)2·8H2O (with M = Zn; Ln = Dy (1), Tb (2) & Gd (3) and M = Cu; Ln = Dy (4), Tb (5) & Gd (6)) and [Ni3Ln3(H2O)3(mpko)9(O2)(NO3)3](ClO4)·3CH3OH·3CH3CN (Ln = Dy (7), Tb (8), and Gd (9)) [mpkoH = 1-(pyrazin-2-yl)ethanone oxime]. All these complexes possess a peroxide ligand that bridges the {Ln III3 } triangle in a μ3-η3:η3 fashion and the oxygen atoms/oxime of co-ligands that connect each MII ion to the {Ln III3 } triangle. Through our computational studies, we tried to find the key role of the peroxide bridge and how it affects the SMM and SMT behavior of these complexes. Primarily, ab initio Complete Active Space Self-Consistent Field (CASSCF) SINGLE_ANISO + RASSI-SO + POLY_ANISO calculations were performed on 1, 2, 4, 5, 7, and 8 to study the anisotropic behavior of each Ln(III) ion, to derive the magnetic relaxation mechanism and to calculate the LnIII–LnIII and CuII/NiII–LnIII magnetic coupling constants. DFT calculations were also performed to validate these exchange interactions (J) by computing the GdIII–GdIII and CuII/NiII–GdIII interactions in 3, 6, and 9. Our calculations explained the experimental magnetic relaxation processes and the magnetic exchange interactions for all the complexes, which also strongly imply that the peroxide bridge plays a role in the SMM behavior observed in these systems. On the other hand, this peroxide bridge does not support the SMT behavior. To investigate the effect of bridging ions in {M3Ln3} systems, we modeled a {Zn II3 Dy III3 } complex (1a) with a hydroxide ion replacing the bridged peroxide ion in complex 1 and considered a hydroxide-bridged {Co III3 Dy III3 } complex (10) having the formula [Co3Dy3(OH)4(OOCCMe3)6(teaH)3(H2O)3](NO3)2·H2O. We discovered that as compared to the LoProp charges of the peroxide ion, the greater negative charges on the bridging hydroxide ion reduce quantum tunneling of magnetization (QTM) effects, enabling more desirable SMM characteristics and also leading to good SMT behavior. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. It includes a list of papers featured in the issue, covering topics such as the photothermal weak absorption of a crystal, halogen bonding proclivity in cocrystals, and the structure and electrical properties of doped single crystals. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document also mentions approved training courses offered by the society. [Extracted from the article]

Two isoreticular lanthanide metal–organic frameworks (Ln-MOFs), {[Ln2(H2O)6(H2dobdc)6·12H2O}n (Ln = Tb3+ and Gd3+); H4dobdc = 2,5-di-hydroxy-benzene-1,4-di-carboxylic acid), constructed from a hydroxy-functionalized dicarboxybenzene were synthesized and structurally characterized. Single-crystal X-ray crystallography reveals that the two Ln-MOFs were constructed from Ln3+ dimers as secondary building units, which were linked by H2dobdc2− ligands to form three-dimensional (3D) frameworks featuring pcu topology. Interestingly, 1D triangular porous channels were formed in the frameworks with a high density of coordinated and guest water molecules and hydroxy-containing inwall, which provide a hydrophilic and highly oxygenated environment. Magnetic studies indicated the Tb(III) analogue exhibited slow relaxation of magnetization under an applied static field of 2 kOe while the Gd(III) MOF displayed the magnetocaloric effect (MCE) with a magnetic entropy change of 19.5 J kg−1 K−1. At 55 °C under 98% RH, impedance spectroscopy indicated that the Ln-MOFs exhibit high proton conductivities up to 1.63 × 10−2 and 2.51 × 10−2 S cm−1 through the vehicle mechanism, suggesting that the two are highly proton-conducting Ln-MOFs. This work not only demonstrates two rare magnetic-electrical bifunctional Ln-MOFs with high proton-conduction and interesting magnetic properties but also provides potential design guidelines for high-performance Ln-MOF based proton conductors. [ABSTRACT FROM AUTHOR]

We used ac-susceptibility measurements to study the superspin relaxation in Fe3O4/Isopar M nanomagnetic fluids of different concentrations. Temperature-resolved data collected at different frequencies, χ″ vs. T|f, reveal magnetic events both below and above the freezing point of the carrier fluid (TF = 197 K): χ″ shows peaks at temperatures Tp1 and Tp2 around 75 K and 225 K, respectively. Below TF, the Néel mechanism is entirely responsible for the superspin relaxation (as the carrier fluid is frozen), and we found that the temperature dependence of the relaxation time, τN(Tp1), is well described by the Dorman–Bessais–Fiorani (DBF) model: τ N T = τ r exp ⁡ E B + E a d k B   T . Above TF, both the internal (Néel) and the Brownian superspin relaxation mechanisms are active. Yet, we found evidence that the effective relaxation times, τeff, corresponding to the Tp2 peaks observed in the denser samples do not follow the typical Debye behavior described by the Rosensweig formula 1 τ e f f = 1 τ N + 1 τ B . First, τeff is 5 × 10−5 s at 225 K, almost three orders of magnitude more that its Néel counterpart, τN~8 × 10−8 s, estimated by extrapolating the above-mentioned DBF analysis. Thus, 1 τ N ≫ 1 τ e f f , which is clearly not consistent with the Rosensweig formula. Second, the observed temperature dependence of the effective relaxation time, τeff(Tp2), is excellently described by τ B − 1 T = T γ 0 exp ⁡ − E ′ k B T − T 0 ′ , a model solely based on the hydrodynamic Brown relaxation, τ B (T) = 3 η T V H k B T , combined with an activation law for the temperature variation of the viscosity, η T = η 0 exp ⁡ E ′ / k B (T − T 0 ′ . The best fit yields γ 0 = 3 η V H k B = 1.6 × 10−5 s·K, E′/kB = 312 K, and T0′ = 178 K. Finally, the higher temperature Tp2 peaks vanish in the more diluted samples (δ ≤ 0.02). This indicates that the formation of larger hydrodynamic particles via aggregation, which is responsible for the observed Brownian relaxation in dense samples, is inhibited by dilution. Our findings, corroborating previous results from Monte Carlo calculations, are important because they might lead to new strategies to synthesize functional magnetic ferrofluids for biomedical applications. [ABSTRACT FROM AUTHOR]

Among the recent developments in metal–organic frameworks (MOFs), porous two-dimensional (2D) MOFs have garnered attention due to providing key technical supports, important energy-saving measures and precise chemical sensors for the green and sustainable society. Herein, two rare porous 2D Dy3+ MOFs, namely [Dy4L6(DMA)2(H2O)3]·7DMA (1, DMA = N,N-dimethylacetamide) and [Dy2L3(DMF)2]·DMF (2, DMF = N,N-dimethylformamide), have been successfully synthesized from reaction with 4,4′-(1,2-diphenylethene-1,2-diyl) dibenzoic acid (H2L) under different solvent systems. The main distinctions between the crystal structures of 1 and 2 arise from the differing solvent molecules residing within the pores which interact with the surrounding frameworks. These effects lead to different sizes of 1D channels. Importantly, different solvents of coordinated/free DMA molecules in 1 and DMF molecules in 2 induce the conversion of magnetic dynamics. Compound 1 exhibits obvious slow magnetic relaxation behavior under 0 Oe dc field, while zero-field out-of-phase signals of 2 exhibit no peaks in the whole temperature range. Compound 1 was magnetically characterized as a new example that the slow magnetic relaxation process can be observed in a 2D Dy3+ layer with 1D channels. Theoretical analysis based on ab initio calculation provides interpretations of magnetic observation. Additionally, compounds 1 and 2 have been tested as efficient fluorescent sensors for Fe3+ ions with high selectivity and sensitivity. The fluorescence quenching of 1 and 2 was demonstrated by an approximately 90% reduction in the emission intensity upon binding to Fe3+ ions. The emission intensities of 1 and 2 at 464 nm and 443 nm have shown linear responses to Fe3+ ion concentration with detection limits of 4.51 × 106 ppb and 6.90 × 106 ppb. [ABSTRACT FROM AUTHOR]

In the present work, we have explored a series of unsaturated hexa-18-crown-6 (U18C6) ligands towards designing highly anisotropic Dy(III) based single-ion magnets (SIMs) with the general formula [Dy(U18C6)X2]+ (where U18C6 = [C12H12O6] (1), [C12H12S6] (2), [C12H12Se6] (3), [C12H12O4S2] (4), [C12H12O4Se2] (5) and X = F, Cl, Br, I, OtBu and OSiPh3). By analysing the electronic structure, bonding and magnetic properties, we find that the U18C6 ligands prefer stabilising the highly symmetric eight-coordinated hexagonal bipyramidal geometry (HBPY-8), which is the source of the near-Ising type anisotropy in all the [Dy(U18C6)X2]+ complexes. Moreover, the ability of sulfur/selenium substituted U18C6 ligands to stabilize the highly anisotropic HBPY-8 geometry makes them more promising towards engineering the equatorial ligand field compared to substituted saturated 18C6 ligands where the exodentate arrangement of the S lone pairs results in low symmetry. Magnetic relaxation analysis predicts a record barrier height over 2700 K for [Dy(C12H12O6)F2]+ and [Dy(C12H12S6)X2]+ (where X = F, OtBu and OSiPh3) complexes, nearly 23% higher than those of the top performing Dy(III) based SIMs in the literature. [ABSTRACT FROM AUTHOR]

The enantiomerically pure Schiff base ligands H2L‐S and H2L‐R yield chiral heterometallic dodecanuclear complexes of the form [Cu8Ln4(OH)8(OMe)4(O2CBut)8(L‐S or L‐R)4(H2O)4] where LnIII=Gd (1S), Tb (2S), Dy (3S, 3R), Ho (4S, 4R), Er (5S) or Y (6S, 6R) and H2L=(S or R)‐2‐{[(1‐hydroxypropan‐2‐yl)imino]methyl}‐6‐methoxyphenol. The complexes are isomorphous and crystallize in the non‐centrosymmetric polar space group C2 in enantiomeric conformation. The chirality of the Schiff base ligands originates from the respective S‐ or R‐ enantiomer of 2‐aminopropan‐1‐ol, is imparted to the complexes and to the crystals that belong to non‐centrosymmetric space group. The chirality and enantiomeric conformation of all complexes are retained in dmso solutions as confirmed by Circular Dichroism spectra which consist of mirror images, expected for enantiomeric pairs. All complexes consist of four distorted cubane‐like subunits [Cu2Ln2(μ3‐OH)2(μ3‐OMe)(μ3‐OR)], which share the LnIII ions and result in a cyclic distorted tetragonal arrangement; each edge of the {LnIII4} quadrilateral is occupied by two μ‐OH− ions that further bridge to a CuII ion. Magnetic susceptibility measurements revealed ferromagnetic interactions for 3S with LnIII=Dy and antiferromagnetic interactions for all other complexes. AC susceptibility data of 3S under 1 kOe external dc field indicate slow magnetic relaxation phenomena below 2 K. [ABSTRACT FROM AUTHOR]

Investigating proton transport at the interface in an excited state facilitates the mechanistic investigation and utilization of nanomaterials. However, there is a lack of suitable tools for in-situ and interfacial analysis. Here we addresses this gap by in-situ observing the proton transport of graphene quantum dots (GQDs) in an excited state through reduction of magnetic resonance relaxation time. Experimental results, utilizing 0.1 mT ultra-low-field nuclear magnetic resonance relaxometry compatible with a light source, reveal the light-induced proton dissociation and acidity of GQDs' microenvironment in the excited state (Hammett acidity function: –13.40). Theoretical calculations demonstrate significant acidity enhancement in –OH functionalized GQDs with light induction (p K a * = –4.62, stronger than that of H2SO4). Simulations highlight the contributions of edge and phenolic –OH groups to proton dissociation. The light-induced superacidic microenvironment of GQDs benefits functionalization and improves the catalytic performances of GQDs. Importantly, this work advances the understanding of interfacial properties of light-induced sp2–sp3 carbon nanostructure and provides a valuable tool for exploring catalyst interfaces in photocatalysis. Understanding interfacial proton transport in an excited state is crucial for catalytic and diagnostic applications of nanomaterials. Here, the authors combine ultra-low-field NMR relaxometry with a light source to study the light-induced proton dissociation of graphene quantum dots. [ABSTRACT FROM AUTHOR]

Two novel Ce(III) metal organic frameworks (MOFs) with formulas [Ce(5Meip)(H-5Meip)]nGR-MOF-17 and [CeCl(5Meip)(DMF)]nGR-MOF-18 (5Meip = 5-methylisophthalate, DMF = N,N-dimethylformamide) have been synthesized, forming 3-dimensional frameworks. Magnetic measurements show that both compounds present field-induced slow magnetic relaxation under a small applied dc field. For GR-MOF-17, the temperature dependence of relaxation times is best described by a Raman mechanism, whereas for GR-MOF-18, relaxation occurs through a combination of Raman and local-mode pathways. Moreover, when avoiding short Ce⋯Ce interactions by magnetic dilution in GR-MOF-17@La and GR-MOF-18@La, only the local-mode mechanism is responsible for magnetic relaxation. Photophysical studies show the occurrence of ligand-centred luminescence in both compounds and phosphorescence emission at low temperature for GR-MOF-17. [ABSTRACT FROM AUTHOR]

Switchable spin dynamic properties in single-molecule magnets (SMMs) via an applied stimulus have applications in single-molecule devices. Many SMMs containing heavy lanthanoid ions with strong uniaxial magnetic anisotropy have been reported to exhibit SMM characteristics in the absence of an external magnetic field. On the other hand, SMMs containing light lanthanoid cerium(III) (Ce3+) ions exhibit field-induced slow magnetic relaxation. We investigated the chemical conversion of a diamagnetic Ce4+ ion (4f0) to a paramagnetic Ce3+ ion (4f1) in Ce-phthalocyaninato double-decker complexes (TBA+[Ce(obPc)2]− (1) and TBA+[Ce(Pc)2]− (2)) which exhibit field-induced SMM behaviour due to a 4f1 system. The phthalocyaninato ligands with electron-donating substituents (obPc2− = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato) in 1 have a significant effect on the valence state of the Ce ion, which is reflected in its magnetic properties due to the mixed valence state of the Ce ion. Given that Ce double-decker complexes with π-conjugated ligands undergo intramolecular electron transfer (IET) to the Ce ion mixed valence state, characterised by a mixture of 4f0 and 4f1 configurations, we examined the dynamic disorder inherent in IET influencing magnetic relaxation. [ABSTRACT FROM AUTHOR]

Two lanthanide complexes with formulae [DyIII(LN5)(pentafluoro-PhO)3] (1) and [DyIII(LN5)(2,6-difluoro-PhO)2](BPh4) (2) (LN5 = 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadecal (19),2,13,15,17-pentaene) were structurally and magnetically characterized. DyIII ions lie in the cavity of a five coordinate nitrogen macrocycle, and in combination with the introduction of multi-fluorinated monodentate phenoxyl coligands a high axiality coordination symmetry is built. Using the pentafluorophenol co-ligand, complex 1 with a D2d coordination environment, is obtained and displays moderate single-molecule magnets (SMMs) behavior. When difluorophenol co-ligands were used, a higher local axisymmetric pentagonal bipyramidal coordination geometry was observed in complex 2, which displays apparent slow magnetic relaxation behavior with a hysteresis temperature of up to 5 K. Further magnetic studies of diluted samples combined with ab initio calculations indicate that the high axiality plays a crucial role in suppressing quantum tunneling of magnetization (QTM) and consequently results in good slow magnetic relaxation behavior. Different fluoro-substituted phenoxyl co-ligands have phenoloxy oxygen atoms with different electrostatic potentials as well as a different number of phenoloxy coligands along the magnetic axis, resulting in different ligand field strengths and coordination symmetries. [ABSTRACT FROM AUTHOR]

AC susceptibility measurements of [FeIII(L5)(NCSe)] reveal a field supported slow magnetic relaxation. On cooling, the relaxation time of the high-frequency fraction decreases which is a sign of reciprocating thermal behaviour. The relaxation time for the low-frequency mode at T = 2.0 K is as high as τ(LF) = 2.0 s. [ABSTRACT FROM AUTHOR]

The early stages of winter wheat (Triticum aesti- vum L.) seed hydration were monitored in order to improve our understanding of the molecular mechanisms of drought resistance. Investigations were carried out using gaseous phase hydration kinetics, sorption isotherm, and 1H-NMR relaxometry. Hydration kinetics have shown that the mass increase could be fitted with a single exponential function. Two fractions of bound water were distinguished: very tightly bound water, Δm/m0 = 0.082 ± 0.016, and the tightly bound water fraction, Δm/m0 = 0.048 ± 0.033, with a hydration time t h 1 = (62 ± 23) h. The standard Dent’s model which was used to fit the experimental data, was successfully applied but only for values of relative humidity smaller than h < 0.9. The sorption isotherm was better fitted using the generalized Dent’s model, with the value of the b parameter equal to 0.947, the mass of the water saturating primary water binding sites equal to ΔM/m0 = 0.0209, and the fraction of unoccupied binding sites at h = 1 equal to 1/b1 = 0.104%. Proton free induction decays regi- stered for dry samples up to hydration level Δm/m0 = 0.128 were better described by the Abragam function, whereas for a higher hydration level the Gaussian function sufficiently described the proton signal of the samples. [ABSTRACT FROM AUTHOR]

Imidazolium salts with complex anions [Co2Li2(Piv)8]2– are formed as undesirable products of the reactions of heterometallic compound [Co2Li2(Piv)6(Py)2] with N-heterocyclic carbenes ItBu and IPr. The study of the magnetic properties of complex (HItBu)2[Co2Li2(µ2-Piv)6(κ1-Piv)2] shows that this compound is a single molecule magnet. Slow magnetic relaxation in the complex occurs due to a combination of the direct and Raman mechanisms. [ABSTRACT FROM AUTHOR]

We used magnetic and synchrotron X-ray diffraction measurements to investigate the possibility of tuning the strength of magnetic interparticle interactions in nanoparticle ensembles via chemical manipulation. Our main result comes from temperature-resolved in-phase ac-susceptibility data collected on 8 nm average-diameter Ni0.25Zn0.75Fe2O4 (Ni25) and Ni0.5Zn0.5Fe2O4 (Ni50) nanoparticles at different frequencies, χ′ vs. T|f. We found that the relative peak temperature variation per frequency decade, ϕ = ∆ T T · ∆ l o g (f) —a known measure of interparticle interaction strength—exhibits a four-fold increase, from ϕ = 0.04 in Ni50 to ϕ = 0.16 in Ni25. This corresponds to a fundamental change in the nanoparticles' superspin dynamics, as proven by the fit of phenomenological models to magnetic relaxation data. Indeed, the Ni25 ensemble exhibits superparamagnetic behavior, where the temperature dependence of the superspin relaxation time, τ, is described in the Dorman–Bessais–Fiorani (DBF) model: τ T = τ r exp ⁡ E B + E a d k B T ,   with parameters τr = 4 × 10−12 s, and (EB + Ead)/kB = 1473 K. On the other hand, the nanoparticles in the Ni50 ensemble freeze collectively upon cooling in a spin-glass fashion according to a critical dynamics law: τ (T) = τ 0 T T g − 1 z ν , with τ0 = 4 × 10−8 s, Tg = 145 K, and zν = 7.2. Rietveld refinements against powder X-ray diffraction data reveal the structural details that underlie the observed magnetic behavior: an indirect cation replacement mechanism by which non-magnetic Zn ions are incorporated in the tetrahedral sites of the inverse spinel. [ABSTRACT FROM AUTHOR]