One-dimensional Antiferromagnetic Chain Research Articles

Synthesis, coordination modes, structures, and magnetic properties of halogen-substituted 2-hydroxypyridine copper(II) chloride coordination compounds

A family of 6-X-2-hydroxyprydine/pyridone (6-X-2-HOpy/pyridone) Cu(II) compounds, [Cu(6-X-2-HOpy)2Cl2] (1 X = F; 2 X = Cl) and [(6-X-2-pyridone)CuCl(μ-Cl)]2 (3 X = Cl; 4 X = Br), has been prepared. Solution-based infrared spectra displayed a correlation between tautomeric state, primarily driven by halogen identity, and coordination mode with neutral nitrogen coordination mode favored as Br ≪ Cl < F. The tautomeric state of 6-Cl-2-HOpy is influenced by metal ion concentration (M) with lactam concentration increasing as M increases. Compound 1 has F–F contacts less than the sum of the van der Waals radii but falls outside of the typical halogen bonding angle parameters, R–X•••Y = R–Y•••X = 138.2°. Compounds 1 and 2 exhibit weak antiferromagnetic exchanges, fit with a one-dimensional quantum Heisenberg antiferromagnetic linear chain (1D-QHAF) model and J/kB = −1.99(1) K and −0.92(7) K, respectively. Compounds 3 and 4 exhibit a dominating ferromagnetic exchange and an antiferromagnetic exchange and were qualitatively fit to a ferromagnetic linear chain with an interchain interaction model. This model does not accurately represent the physical parameters of the system and was used to show that both exchanges exist and are nontrivial.

Spin chirality driven by the Dzyaloshinskii–Moriya interaction in one-dimensional antiferromagnetic chain

Dzyaloshinskii–Moriya (DM) interactions cause many interesting physical features, such as topologically nontrivial magnetic skyrmions and chiral domain walls. These interactions become more pronounced in low-dimensional systems. We investigated a one-dimensional Heisenberg spin-1/2 chain with an asymmetric DM interaction. The results show that, upon applying a nonzero DM interaction, the Néel ground state transitions to a spin chiral phase. Moreover, using the mean-field approximation, we obtain the dispersion of the energy spectrum, from which the z-axis spin chirality is calculated as a function of the strength of the DM interaction for low-lying excitations. The results indicate that the DM interaction facilitates chirality for Dz ≤ J and induces a spin-gapped chiral state.

Emergence of Spinons in Layered Trimer Iridate Ba_{4}Ir_{3}O_{10}.

Spinons are well known as the elementary excitations of one-dimensional antiferromagnetic chains, but means to realize spinons in higher dimensions is the subject of intense research. Here, we use resonant x-ray scattering to study the layered trimer iridate Ba_{4}Ir_{3}O_{10}, which shows no magnetic order down to 0.2K. An emergent one-dimensional spinon continuum is observed that can be well described by XXZ spin-1/2 chains with a magnetic exchange of ∼55 meV and a small Ising-like anisotropy. With 2% isovalent Sr doping, magnetic order appears below T_{N}=130 K along with sharper excitations in (Ba_{1-x}Sr_{x})_{4}Ir_{3}O_{10}. Combining our data with exact diagonalization calculations, we find that the frustrated intratrimer interactions effectively reduce the system into decoupled spin chains, the subtle balance of which can be easily tipped by perturbations such as chemical doping. Our results put Ba_{4}Ir_{3}O_{10} between the one-dimensional chain and two-dimensional quantum spin liquid scenarios, illustrating a new way to suppress magnetic order and realize fractional spinons.

Open-framework transition metal fluorophosphates with one-dimensional antiferromagnetic chains

Two open frameworks fluorophosphates materials (NH4)2M2F2(PO4)(PO3F)OH (M ​= ​Fe and V) have been synthesized via fluoride-rich hydrothermal routes at 493 ​K. The two isostructural compounds revealed three-dimensional (3D) frameworks, composed of trans-MO4F2, cis-MO4F2, trans-MO2F2(OH)2 octahedra, and PO4, PO3F and NH4 tetrahedra. The anionic backbone of (NH4)2M2F2(PO4)(PO3F)OH consists of a series of parallel zigzag [M2F2O7OH] chains cross-connected with each other, bridged by PO4 tetrahedra within two-dimensional (2D) layer, and bridged by PO3F groups vertical to 2D layer. It generates a three 3D open framework. The XPS spectra revealed the valence of Fe and V are III in the corresponding compounds. The isostructural compounds feature transition metal zigzag chains, which promotes robust antiferromagnetic (AFM) interactions in (NH4)2Fe2F2(PO4)(PO3F)OH in contrast to weak AFM in (NH4)2V2F2(PO4)(PO3F)OH.

Discrete Open-Shell Tris(bipyridinium radical cationic) Inclusion Complexes in the Solid State.

The solid-state properties of organic radicals depend on radical-radical interactions that are influenced by the superstructure of the crystalline phase. Here, we report the synthesis and characterization of a substituted tetracationic cyclophane, cyclobis(paraquat-p-1,4-dimethoxyphenylene), which associates in its bisradical dicationic redox state with the methyl viologen radical cation (MV•+) to give a 1:1 inclusion complex. The (super)structures of the reduced cyclophane and this 1:1 complex in the solid state deviate from the analogous (super)structures observed for the reduced state of cyclobis(paraquat-p-phenylene) and that of its trisradical tricationic complex. Titration experiments reveal that the methoxy substituents on the p-phenylene linkers do not influence binding of the cyclophane toward small neutral guests-such as dimethoxybenzene and tetrathiafulvalene-whereas binding of larger radical cationic guests such as MV•+ by the reduced cyclophane decreases 10-fold. X-ray diffraction analysis reveals that the solid-state superstructure of the 1:1 complex constitutes a discrete entity with weak intermolecular orbital overlap between neighboring complexes. Transient nutation EPR experiments and DFT calculations confirm that the complex has a doublet spin configuration in the ground state as a result of the strong orbital overlap, while the quartet-state spin configuration is higher in energy and inaccessible at ambient temperature. Superconducting quantum interference device (SQUID) measurements reveal that the trisradical tricationic complexes interact antiferromagnetically and form a one-dimensional Heisenberg antiferromagnetic chain along the a-axis of the crystal. These results offer insights into the design and synthesis of organic magnetic materials based on host-guest complexes.

Magnetic properties of the one-dimensional S=32 Heisenberg antiferromagnetic spin-chain compound Na2Mn3O7

We have performed magnetic susceptibility $(\ensuremath{\chi})$, heat capacity $({C}_{p})$, and nuclear magnetic resonance (NMR) measurements on the layered compound ${\mathrm{Na}}_{2}{\mathrm{Mn}}_{3}{\mathrm{O}}_{7}$ in which the magnetic ${\mathrm{Mn}}^{4+}$ ions constitute a maple-leaf lattice. At high temperature, $\ensuremath{\chi}$ follows the Curie-Weiss (CW) law with CW temperature as high as 152 K and ${\mathrm{Mn}}^{4+}$ ions are found to be in the high-spin state $(S=\frac{3}{2})$. With decreasing temperature, $\ensuremath{\chi}$ passes through a broad maximum at 115 K and decreases rapidly at low temperature. A similar broad peak appears at around 62 K in the magnetic contribution to heat capacity $({C}_{m})$. The temperature dependence of $\ensuremath{\chi}$ and ${C}_{m}$ are the characteristics of an one-dimensional Heisenberg antiferromagnetic spin chain with a nonmagnetic ground state. The obtained values of spin-gap energy $({\mathrm{\ensuremath{\Delta}}}_{s})$ and nearest-neighbor antiferromagnetic exchange coupling $(J)$ are 28 and 27 K, respectively. There is no evidence of a long-range magnetic ordering down to 2 K in heat capacity data, in agreement with spin-singlet ground state. These observations are further corroborated by $^{23}\mathrm{Na}$ NMR studies through measurements of both the NMR shift and the spin-lattice relaxation rate.

Magnonic analog of the Edelstein effect in antiferromagnetic insulators

We investigate the nonequilibrium spin polarization due to a temperature gradient in antiferromagnetic insulators, which is the magnonic analogue of the inverse spin-galvanic effect of electrons. We derive a linear response theory of a temperature-gradient-induced spin polarization for collinear and noncollinear antiferromagnets, which comprises both extrinsic and intrinsic contributions. We apply our theory to several noncentrosymmetric antiferromagnetic insulators, i.e., to a one-dimensional antiferromagnetic spin chain, a single layer of kagome noncollinear antiferromagnet, e.g., $\text{KFe}_3(\text{OH})_6(\text{SO}_4)_2$, and a noncollinear breathing pyrochlore antiferromagnet, e.g., LiGaCr$_4$O$_8$. The shapes of our numerically evaluated response tensors agree with those implied by the magnetic symmetry. Assuming a realistic temperature gradient of $10 \text{K}/\text{mm}$, we find two-dimensional spin densities of up to $\sim 10^6\hbar/\text{cm}^2$ and three-dimensional bulk spin densities of up to $\sim 10^{14}\hbar/\text{cm}^3$, encouraging an experimental detection.

Synthesis and Characterization of Sodium-Iron Antimonate Na2FeSbO5: One-Dimensional Antiferromagnetic Chain Compound with a Spin-Glass Ground State.

A new oxide, sodium-iron antimonate, Na2FeSbO5, was synthesized and structurally characterized, and its static and dynamic magnetic properties were comprehensively studied both experimentally by dc and ac magnetic susceptibility, magnetization, specific heat, electron spin resonance (ESR) and Mössbauer measurements, and theoretically by density functional calculations. The resulting single-crystal structure (a = 15.6991(9) Å; b = 5.3323 (4) Å; c = 10.8875(6) Å; S.G. Pbna) consists of edge-shared SbO6 octahedral chains, which alternate with vertex-linked, magnetically active FeO4 tetrahedral chains. The 57Fe Mössbauer spectra confirmed the presence of high-spin Fe3+ (3d5) ions in a distorted tetrahedral oxygen coordination. The magnetic susceptibility and specific heat data show the absence of a long-range magnetic ordering in Na2FeSbO5 down to 2 K, but ac magnetic susceptibility unambigously demonstrates spin-glass-type behavior with a unique two-step freezing at Tf1 ≈ 80 K and Tf2 ≈ 35 K. Magnetic hyperfine splitting of 57Fe Mössbauer spectra was observed below T* ≈ 104 K (Tf1 < T*). The spectra just below T* (Tf1 < T < T*) exhibit a relaxation behavior caused by critical spin fluctuations, indicating the existence of short-range correlations. The stochastic model of ionic spin relaxation was used to account for the shape of the Mössbauer spectra below the freezing temperature. A complex slow dynamics is further supported by ESR data revealing two different absorption modes presumably related to ordered and disordered segments of spin chains. The data imply a spin-cluster ground state for Na2FeSbO5.

Antiferromagnetic NiO atomic chains for information storage and the enhancement of inter-chain spin coupling by CO adsorption

One-dimensional antiferromagnetic atomic chains have potential applications in information storage and spintronics devices. NiO chains have been assembled on the Ni(110) single crystal surface, and the antiferromagnetic spin order has been determined by the first-principles calculations. Scanning tunneling microscope simulation clearly distinguishes two types of Ni with opposite spin-orientations. Therefore, the information carried by such system is possible to be read out. Furthermore, we have introduced the CO molecules, which zipper the neighboring NiO chains and greatly enhance the inter-chain spin coupling. The incorporation of CO has been verified by the low energy electron diffraction and the infrared spectroscopy.

Spin triplet ground-state in the copper hexamer compoundsA2Cu3O(SO4)3(A=Na,K)

The compounds A2Cu3O(SO4)3 (A=Na,K) are characterized by copper hexamers which are weakly coupled along the b-axis to realize one-dimensional antiferromagnetic chains below TN=3 K, whereas the interchain interactions along the a- and c-axes are negligible. We investigated the energy-level splittings of the copper hexamers by inelastic neutron scattering below and above TN. The eight lowest-lying hexamer states could be unambiguously assigned and parametrized in terms of a Heisenberg exchange Hamiltonian, providing direct experimental evidence for an S=1 triplet ground-state associated with the copper hexamers. Therefore, the compounds A2Cu3O(SO4)3 serve as novel cluster-based spin-1 antiferromagnets to support Haldane's conjecture that a gap appears in the excitation spectrum below TN, which was verified by inelastic neutron scattering.

Accuracy of the microcanonical Lanczos method to compute real-frequency dynamical spectral functions of quantum models at finite temperatures.

We examine the accuracy of the microcanonical Lanczos method (MCLM) developed by Long etal. [Phys. Rev. B 68, 235106 (2003)PRBMDO0163-182910.1103/PhysRevB.68.235106] to compute dynamical spectral functions of interacting quantum models at finite temperatures. The MCLM is based on the microcanonical ensemble, which becomes exact in the thermodynamic limit. To apply the microcanonical ensemble at a fixed temperature, one has to find energy eigenstates with the energy eigenvalue corresponding to the internal energy in the canonical ensemble. Here, we propose to use thermal pure quantum state methods by Sugiura and Shimizu [Phys. Rev. Lett. 111, 010401 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.010401] to obtain the internal energy. After obtaining the energy eigenstates using the Lanczos diagonalization method, dynamical quantities are computed via a continued fraction expansion, a standard procedure for Lanczos-based numerical methods. Using one-dimensional antiferromagnetic Heisenberg chains with S=1/2, we demonstrate that the proposed procedure is reasonably accurate, even for relatively small systems.

Ground-state properties of the one-dimensional antiferromagnetic chain with frustrated side spins

The properties of the one-dimensional antiferromagnetic chain with frustrated side spins are studied by means of the spin wave theory, the exact diagonalization method and the density matrix renormalization group method. The results show that the Lieb–Mattis type ferrimagnetic state is always the ground state when α<αc1. The system undergoes a first-order phase transition accompanied by a spontaneous symmetry breaking and its acoustic excitation spectrum softens completely near k=0 at the critical point αc1. In the intermediate parameter region αc1<α<αc2, the ground state is a nonmagnetic state called dimer-tetramer state with a small spin gap. A gapped-gapless Berezinskii-Kosterlitz-Thouless phase transition occurs at another critical point αc2 beyond which the nonmagnetic dimer–monomer state becomes the ground state. The value of the critical point αc2 can be precisely determined not only by the level-spectroscopy method, but also the method based on comparing the magnitude of the two types of correlation functions and the method of a scaling analysis of the gap.

Realization of a Strained Atomic Wire Superlattice.

A superlattice of strained Au-Si atomic wires is successfully fabricated on a Si surface. Au atoms are known to incorporate into the stepped Si(111) surface to form a Au-Si atomic wire array with both one-dimensional (1D) metallic and antiferromagnetic atomic chains. At a reduced density of Au, we find a regular array of Au-Si wires in alternation with pristine Si nanoterraces. Pristine Si nanoterraces impose a strain on the neighboring Au-Si wires, which modifies both the band structure of metallic chains and the magnetic property of spin chains. This is an ultimate 1D version of a strained-layer superlattice of semiconductors, defining a direction toward the fine engineering of self-assembled atomic-scale wires.

One-dimensional quantum antiferromagnetism in thep-orbitalCsO2compound revealed by electron paramagnetic resonance

Recently it was proposed that the orbital ordering of $\pi_{x,y}^*$ molecular orbitals in the superoxide CsO$_2$ compound leads to the formation of spin-1/2 chains below the structural phase transition occuring at $T_{\rm{s1}}=61$~K on cooling. Here we report a detailed X-band electron paramagnetic resonance (EPR) study of this phase in CsO$_2$ powder. The EPR signal appears as a broad line below $T_{\rm{s1}}$, which is replaced by the antiferromagnetic resonance below the N\'{e}el temperature $T_{\rm N}=8.3$~K. The temperature dependence of the EPR linewidth between $T_{\rm{s1}}$ and $T_{\rm{N}}$ agrees with the predictions for the one-dimensional Heisenberg antiferromagnetic chain of $S=1/2$ spins in the presence of symmetric anisotropic exchange interaction. Complementary analysis of the EPR lineshape, linewidth and the signal intensity within the Tomonaga-Luttinger liquid (TLL) framework allows for a determination of the TLL exponent $K=0.48$. Present EPR data thus fully comply with the quantum antiferromagnetic state of spin-1/2 chains in the orbitally ordered phase of CsO$_2$, which is, therefore, a unique $p-$orbital system where such a state could be studied.

Magnetic properties of manganese based one-dimensional spin chains.

We have correlated the structure-property relationship of three manganese-based inorganic-organic hybrid structures. Compound 1, [Mn2(OH-BDC)2(DMF)3] (where BDC = 1,4-benzene dicarboxylic acid and DMF = N,N'-dimethylformamide), contains Mn2O11 dimers as secondary building units (SBUs), which are connected by carboxylate anions forming Mn-O-C-O-Mn chains. Compound 2, [Mn2(BDC)2(DMF)2], contains Mn4O20 clusters as SBUs, which also form Mn-O-C-O-Mn chains. In compound 3, [Mn3(BDC)3(DEF)2] (where DEF = N,N'-diethylformamide), the distorted MnO6 octahedra are linked to form a one-dimensional chain with Mn-O-Mn connectivity. The magnetic properties were investigated by means of magnetization and heat capacity measurements. The temperature dependent magnetic susceptibility of all the three compounds could be nicely fitted using a one-dimensional S = 5/2 Heisenberg antiferromagnetic chain model and the value of intra-chain exchange coupling (J/k(B)) between Mn(2+) ions was estimated to be ∼1.1 K, ∼0.7 K, and ∼0.46 K for compounds 1, 2, and 3, respectively. Compound 1 does not undergo any magnetic long-range-order down to 2 K while compounds 2 and 3 undergo long-range magnetic order at T(N) ≈ 4.2 K and ≈4.3 K, respectively, which are of spin-glass type. From the values of J/k(B) and T(N) the inter-chain coupling (J(⊥)/k(B)) was calculated to be about 0.1J/k(B) for both compounds 2 and 3, respectively.

An unpredictable chain ion-pairing complex {[Cu(terpy)CN]PCQ}n

The in-situ reaction of LiTCNQ (TCNQ=7,7,8,8-tetracyano-pquinodimethane) and [Cu2(terpy)2(H2O)2(ta)][ClO4]2 (terpy=2,2′,2″-terpyridine, ta=terephthalate) forms an unpredictable complex {[Cu(terpy)CN]PCQ}n (1) (PCQ=p-tricyanovinylphenyldicyanomethide). X-ray crystallographic analysis and magnetic investigation show that 1 behaves as one-dimensional (1D) antiferromagnetic chains. The production of 1 proves that cyanide is formed in the process of PCQ− formation from TCNQ−.

Suitability of chromium phthalocyanines to test Haldane's conjecture: First-principles calculations

We have studied the intrachain magnetic interactions in chromium phthalocyanine (CrPc, spin 2) for a wide range of chain structural parameters using hybrid exchange density functional theory. A comparison of the computed interchain and intrachain exchange interactions and zero-field splitting shows that many of the chain structures including those in the α and η phases are suitable one-dimensional antiferromagnetic chains of integer spins for testing Haldane’s conjecture. In addition, the exchange interaction in CrPc is strongly dependent on the stacking angle and weakly on the sliding angle. The peak value of the exchange interactions is 120 K when the molecules are face on, which is much larger than those in copper phthalocynines. The prediction of the relationship between the computed magnetic properties and geometrical parameters can provide guidance to experimentalists for the applications of CrPc structures in spintronics.

From One-Dimensional Linear Chain to Two-Dimensional Layered Chalcogenides XBi4S7(X = Mn, Fe): Syntheses, Crystal and Electronic Structures, and Physical Properties

Two ternary-layered chalcogenides, MnBi4S7 (1) and FeBi4S7 (2), have been synthesized by using a conventional solid-state reaction method with sealed evacuated quartz tubes. The two isostructural compounds crystallize in the monoclinic space group C2/m (12), with unit cell parameters (1/2) a = 12.916(12)/12.823(19) A, b = 3.970(3)/3.987(6) A, c = 11.0397(15)/11.878(18) A, β = 104.755(14) /104.38(2), and Z = 2 at room temperature. The remarkable structural features of these are the one-dimensional Heisenberg antiferromagnetic (1D HAF) chain, 1∞[XS6], and the two-dimensional [Bi2S3] and [MBi2S4] layers built up from the 1D 1∞[XS6] chain, 1∞[BiS6], and 1∞[BiS5] double chains. Magnetic property measurements indicate strong predominance of antiferromagnetic (AFM) interactions, with Neel temperatures (TN) of 31 K for 1 and 67 K for 2, respectively. The density functional theory (DFT) study indicates that both compounds are indirect-band semiconductors with band gaps of 0.79 eV for 1 and 1.24 eV for 2, respectively.

Quasi-one-dimensional (Q1D) organic Mott insulators based on bent donor molecule EDO-EDSe-TTFVS

A series of conducting quasi-one-dimensional (Q1D) cation radical salts based on a bent donor molecule EDO-EDSe-TTFVS (1), 12ClO4, 12PF6(PhCl)0.25, and 12AsPF6(PhCl)0.25, were obtained via electrocrystallization. These salts show the semiconducting behavior with moderate conductivities up to 4.0Scm−1 and relatively large magnetic susceptibilities of 9×10−4emumol−1. The temperature dependent magnetic susceptibilities of these salts can be well fitted by the one-dimensional Heisenberg antiferromagnetic chain model. In their crystal structures, two donor molecules are crystallographically independent, while they are in the same oxidation state of +0.5 judging from their CC double bond lengths. The donor molecules form columnar stacks composed of donor dimers, and the size of the counter ion plays an important role on the degree of donor molecule dimerization. The electronic bands of these salts substantially split into the upper and lower two bands, and the upper bandwidth (WU) is smaller than on-site Coulomb repulsion of donor dimer (Udimer), WU/Udimer<0.85. These salts are intrinsically Mott insulators.

Seeking Hidden Magnetic Phenomena by Theoretical Means in a Thiooxoverdazyl Adduct

The oxidation of 1,5-dimethyl-3-(2'-pyridyl)-6-thiooxotetrazane (SvdH(3) py) by benzoquinone leads to a 1:1 adduct of 1,5-dimethyl-3-(2'-pyridyl)-6-thiooxoverdazyl radical (Svdpy) with hydroquinone (hq). The single-crystal X-ray diffraction of this adduct at room temperature (RT) shows that the radicals exhibit a slight curvature that leads to the formation of alternating head-to-tail (antiparallel) stacked 1D chains. Moreover, temperature-dependent X-ray measurements at 100, 200, and 303 K reveal that the lateral slippages between the radicals of the stacks |δ(1) | and |δ(2) | vary from 0.64 to 0.78 Å and 0.54 to 0.40 Å between 100 and 303 K. Despite the alternation of the inter-radical distances and lateral slippages, the magnetic susceptibility data can be fitted with excellent agreement using a regular one-dimensional antiferromagnetic chain model with J=-5.9 cm(-1). Wavefunction-based calculations indicate an alternation of the magnetic interaction parameters correlated with the structural analysis at RT. Moreover, they demonstrate that the thermal slippage of the radicals induces a switching of the physical behavior, since the exchange interaction changes from antiferromagnetic (-0.9 cm(-1)) at 100 K to ferromagnetic (1.4 cm(-1)) at 303 K. The theoretical approach thus reveals a much richer magnetic behavior than the analysis of the magnetic susceptibility data and ultimately questions the relevance of a spin-coupled picture based on temperature-independent parameters.