One-dimensional Antiferromagnet Research Articles

Synthesis of [NH4]MnCl2(OAc) and [NH4]2MnCl4(H2O)2 by Solvothermal Dehydration and Structure/Property Correlations in a One-Dimensional Antiferromagnet

The utility of the solvothermal dehydration strategy whereby superheated acetonitrile reacts with water of hydration to form ammonium acetate is demonstrated in the synthesis of [NH(4)]MnCl(2)(OAc), I, and [NH(4)](2)MnCl(4)(H(2)O)(2), II, from MnCl(2).4H(2)O. The structure of I is shown to crystallize in the monoclinic space group C2/c (No. 15) with a = 15.191(6) A, b = 7.044(2) A, c = 13.603(6) A, beta = 107.31 degrees, V = 1389.7(9) cm(-)(1), and Z = 8. The structure of II crystallizes in the space group I4/mmm (No. 139) with a = 7.5250(5) A, b = 8.276(2) A, V = 468.6(1) cm(-)(1), and Z = 2. Both structures exhibit extensive hydrogen bonding that controls both local Mn-Cl bonding and the interchain organization. I is shown to be a one-dimensional Heisenberg antiferromagnet with an intrachain exchange constant J/k = -2.39 K. This structure exhibits exchange coupling intermediate between the well-studied triply and doubly chloride-bridged one-dimensional manganese Heisenberg antiferromagnets. The structure/property correlation demonstrates a linear dependence of the exchange constant on the Mn-Cl-Mn bond angle, alpha, for alpha < 94 degrees.

Spinless fermions versus spin waves in describing antiferromagnetic Heisenberg ladders

We investigate magnetic properties of the spin − 1 2 two-leg Heisenberg ladder antiferromagnet developing two formulations, one of which starts from the Jordan–Wigner transformation along an elaborately ordered path, and the other of which modifies the conventional spin-wave theory so as to restore the sublattice symmetry. The static and dynamic quantities are calculated and a novel field dependence of the nuclear spin-lattice relaxation rate, which is peculiar to one-dimensional spin-gapped antiferromagnets, is pointed out in particular.

Magnetic order and moment distribution in doped spin-chain systems

We consider the effect of doping on the magnetic order in quasi one-dimensional (1D) antiferromagnets. First the detailed magnetic response of finite spin-1/2 chains in the presence of a staggered field is determined, which by itself shows an interesting crossover as function of length and field strength. We can then understand the ordering by including an effective coupling between the chains, which results in a Neel ordered phase at low temperatures, but with a broad distribution of magnetic moments that has to be determined self-consistently.

Linear antiferromagnetism in Ba2CoS3.

Ba(2)CoS(3) is the first example of an inorganic solid containing one-dimensional corner-sharing [Co(2+)-anion] chains, which leads to one-dimensional cooperative antiferromagnetism.

NDMAP: the best material to study the Haldane's prediction

As predicted by Haldane, spin, S=1 one-dimensional (1D) Heisenberg antiferromagnet (HAF) has an energy gap between the singlet ground state and first excited triplet. On application of magnetic field, the triplet state Zeeman splits and the energy of one of the triplet state becomes zero at a critical field, H c. Above H c the system recovers magnetism. Then, we expect that a quasi-1D HAF will show a magnetic long-range ordering (LRO) at low temperatures due to the inter-chain coupling. This field-induced LRO has not been observed before due to complication of the crystal structure in the materials studied so far and/or technical difficulty. From a heat capacity measurement on a single crystal of an S=1 quasi-Q1D HAF, Ni(C 5H 14N 2) 2N 3(PF 6), we found an anomaly at a temperature in finite fields indicating a field-induced phase transition. A magnetic LRO is confirmed by a neutron diffraction measurement on the same sample. The temperature versus magnetic field phase diagram of this compound is constructed and discussed.

Magnetic Dimensionality of the Antiferromagnet CuO

We present evidence for the quasi one-dimensional (1D) antiferromagnetism of CuO in the framework of the Heisenberg model. Our result supports the speculations and conclusions made by earlier authors. We also present experimental evidence which explains the reason for CuO to be a quasi 1D antiferromagnet in spite of appearing to have a 3D structure.

A decoupling-free solid-state NMR quantum computer

We present a decoupling-free solid-state NMR quantum computer with a switchable controlled-NOT gate installed in a one-dimensional antiferromagnet with a spin gap. The gate switching is realized by a local singlet-triplet excitation across the spin gap, which induces a Suhl–Nakamura-type internuclear coupling between control and target qubits. Naive calculation for the coupling strength with some realistic parameters indicates that the coupling can be strong enough to serve as a controlled-NOT gate.

Electron Spin Dynamics in a Spin 1/2 One-Dimensional Heisenberg Antiferromagnet [CuX2(AdH+)2]X2

Electron spin dynamics on a spin 1/2 one-dimensional Heisenberg antiferromagnet, [CuX 2 (AdH + ) 2 )X 2 (X : Cl, Br; Ad : adenine) was studied by 1 H NMR spin-lattice relaxation measurement. 1 H T 1 of [CuBr 2 (AdH + ) 2 ]Br 2 (J = 52.6 K) in the low-temperature region below 25 K was well described by the spin fluctuation relaxation theory proposed by Sachdev.

Crystal Structure and Magnetic Properties of the Quasi-One-Dimensional Quantum Spin System Cu2Cl4·H8C4SO2

The crystal structure of Cu 2 Cl 4 ·H 8 C 4 SO 2 was analyzed by single-crystal X-ray diffraction. This compound consists of the double chain of the edge-sharing octahedra CuCl 5 O. With decreasing temperature, the magnetic susceptibility decreases steeply toward zero below 10 K after exhibiting a broad maximum at 65 K, which is characteristic of the one-dimensional antiferromagnet. The magnetic properties of the present system can be described by the double spin chain model with dominant exchange interactions along the leg. The observed small excitation gap Δ/ k B ≈5.8 K is attributed to the weak exchange alternation along the leg or the weak zig-zag rung interactions. The magnetization curve measured at 1.3 K for the magnetic field parallel to the c -axis shows a discontinuous jump at H t ≈22.8 T indicative of the phase transition of the first order.

Quasi-one-dimensional spin chains in CuSiO3: an EPR study

Temperature dependent EPR studies were performed on a single crystal of CuSiO3.This recently discovered compound is isostructural with the spin-Peierls compound CuGeO3. The EPR signals show different characteristics than those of CuGeO3 and aredue to Cu2+ spins located along quasi one-dimensional chains. For T > 8.2K the spin susceptibility closely follows the predictions of a S=1/2 one-dimensional Heisenberg antiferromagnet with J/kB = 21K. Below T = 8.2K the spin susceptibility immediately drops to zero indicating long range magnetic order.

Magnetic order ofLiMnBO3: A new type of chiral magnetic ground state

$\ensuremath{\beta}\ensuremath{-}{\mathrm{LiMnBO}}_{3}$ crystallizes in a hexagonal lattice and is built up of ${\mathrm{MnO}}_{5}$ chains linked by ${\mathrm{BO}}_{3}$ groups. Magnetic susceptibility shows a broad maximum at 47 K, above which the behavior is typical for a one-dimensional Heisenberg antiferromagnet with $J=5.4 \mathrm{K}.$ Magnetic neutron diffraction reveals a much lower ordering temperature (28.5 K) to give a novel chiral ground state with a magnetic unit cell of $\sqrt{3}{a}_{\mathrm{N}},$ ${2c}_{\mathrm{N}}$ consisting of a mixture of one ferromagnetic ${\mathrm{Mn}}_{3}$ triangle and two normal 120\ifmmode^\circ\else\textdegree\fi{} antiferromagnetic ${\mathrm{Mn}}_{3}$ triangles.

Classical Properties in Spin Dynamics in the S=2 One-Dimensional Heisenberg Antiferromagnet, CsCrCl3

We performed inelastic neutron scattering experiments, in order to investigate the spin dynamics in the S =2 one-dimensional (1D) Heisenberg antiferromagnet, CsCrCl 3 , above the three-dimensional ordering temperature ( T N =16 K). We deduced the static correlation function from the dynamical structure factor. The inverse correlation length showed a linear temperature dependence and was described by quantum and classical theories with the exchange constant determined from the dispersion relation of the magnetic excitations. The temperature dependence of the dynamical structure factor was also determined. We demonstrated that the spin dynamics in CsCrCl 3 above T N is quantitatively well described by classical theory for a 1D Heisenberg antiferromagnetic system.

Dynamics of the quantum one-dimensional Heisenberg antiferromagnet with spin S=1 at low temperature

We report low-temperature dynamic properties of the quantum one-dimensional antiferromagnetic Heisenberg model with spin S=1. The dynamic correlation function is calculated using a procedure that combines a projection operator technique proposed by Reiter and a modified spin wave theory proposed by Takahashi. This modified spin wave theory predicts a temperature-dependent gap whose behavior is compared to the behavior obtained experimentally and also from different approaches. Our calculation suggests that the gap has strong effects on the shape of the dynamical correlation function.

Frequency Dependence of Electron Spin Resonance

ESR in an S = ½ spin system is studied by a direct numerical method calculating the dynamical susceptibility expressed by the Kubo formula. Frequency-dependence of the resonant field is calculated in a one-dimensional antiferromagnet. We find that the frequency-dependence of the resonant field changes according to a relation among the amplitude of the interaction and other external parameters, e.g., temperature and frequency.

Low-energy excitations inNaV2O5

In the (ab) polarized Raman scattering spectra of NaV2O5 single crystals, measured with 647.1 nm laser line at T < Tc, we found two modes at 86, and 126 cm-1 not previously reported. These two modes, together with 66, and 106 cm-1 modes, make an array of four low-energy equidistant modes below the energy onset of the continuum at about 132 cm-1. All four modes are strongly suppressed by increasing Na deficiency, indicating their nonvibrational origin and the existence of a quantum phase transition at critical Na deficiency between 3 and 4%. These results question current understanding of NaV2O5 as quasi one-dimensional Heisenberg antiferromagnet.

Chemical bonding study in Ca substituted Y 2BaNiO 5 by analysis of charge density distribution

Y 2BaNiO 5, along with its Ca-substituted analog Y 2− x Ca x BaNiO 5 (0< x≤0.33), displays peculiar physical properties related to the presence of linear chains of NiO 6 octahedra. These compounds can be considered prototypical Haldane systems and one-dimensional Heisenberg antiferromagnets. In this work, we investigate how the presence of calcium influences the electronic charge distribution and the bond character of these octahedra. The electron density map ρ( r) is derived from powder X-ray diffraction patterns with a novel procedure based upon a correlative use of two methods: Maximum Entropy Method (MEM) and Whole Powder Profile Fitting (WPPF). We compute the Laplacian ∇ 2 ρ( r) at the Bader critical point of the M–O bond; this quantity is shown to be directly related to structural parameters and their dependence upon composition. In particular, the substantial contraction of NiO 6 octahedra with increasing Ca content is related to an Ni–O bond which becomes more ionic as x increases up to x=0.24. On the other hand, covalency becomes stronger above x=0.24, particularly along some Ba–O bonds. Computation of the Shannon entropies confirms the existence of a singularity of the x=0.24 composition, which is a threshold for the re-arrangement of the crystal structure.

Dynamical properties of a gas of solitons in one-dimensional quantum antiferromagnets

The influence of the soliton-magnon coupling on the dynamical properties of quantum antiferromagnets is studied as a function of the external magnetic field and the temperature. The specific case of tetramethyl ammonium manganese chloride is analyzed above and below the transition temperature. The existence of a dissipative regime for the soliton motion is conjectured and its influence on the dynamical structure factor---which might be experimentally detected---is reported.

Quantum linear magnetic chains: structure and magnetic behavior of (2-methylpyrazine)copper(II) nitrate

The X-ray structure, susceptibility and magnetization of (2-methylpyrazine)copper(II) nitrate are reported. The compound crystallizes in the space group Pmna as a coordination polymer of Cu(II) ions bridged by 2-methylpyrazine. The resulting chains are magnetically well isolated and the susceptibility of the compound is well modeled as a one-dimensional Heisenberg antiferromagnet with 2 J=9.5(1) K. High-field magnetization studies to 30 T confirm the value of the exchange constant.

ONE-DIMENSIONAL SPIN-ONE HEISENBERG ANTIFERROMAGNET WITH SINGLE-ION ANISOTROPY IN A MAGNETIC FIELD: SCHWINGER BOSON THEORY

The one-dimensional spin-one Heisenberg antiferromagnet with single-ion anisotropy in the presence of the applied magnetic field is explored in terms of the Schwinger boson mean-field theory. The temperature and anisotropy dependences of the specific heat, the susceptibility and the magnetization are thoroughly discussed. New features of the specific heat as a function of temperature as well as anisotropy are found. A transition from an antiferromagnetic phase to a spin-canting phase is observed, and meanwhile, a schematic phase diagram is proposed.

Low-energy spin dynamics of CuO chains in YBa 2Cu 3O 6+ x

We study the spin fluctuation dynamics of Cu–O chains in the oxygen deficient planes of YBa 2Cu 3O 6+ x . The chains are described by a model including antiferromagnetic interactions between the spins and Kondo-like scattering of the oxygen holes by the copper spins. There are incommensurate spin fluctuations along the direction of the chains. The dynamic structure factor of this system is qualitatively different from that of a quasi one-dimensional localized antiferromagnet due to the presence of itinerant holes. We compute the dynamic structure factor that could be measured in neutron scattering experiments.