1D Antiferromagnets Research Articles

Internal localized eigenmodes on spin discrete breathers in antiferromagnetic chains with on-site easy-axis anisotropy

We investigate internal localized eigenmodes of the linearized equation around spin discrete breathers in 1D antiferromagnets with on-site easy axis anisotropy. The threshold of occurrence of the internal localized eigenmodes has a typical structure in parameter space depending on the frequency of the spin discrete breather. We also performed molecular dynamics simulation in order to show the validity of our linear analysis.

Geometric derivation of nonlinear sigma model for the 1D antiferromagnet

It is argued that a purely geometric derivation of the long-range action for the 1D antiferromagnet is available in terms of a Kahler potential. The derivation allows for a natural extension to the t-J model. In particular, it follows that a relevant long-wavelength action of the t-J model exhibits at least at the SUSY (J=2t) point the su(2∣1) invariance rather than the so(5) one.

Purely Organic Magnetism of Pyridyl-Substituted Stable Thioaminyl Radicals

N-[(4-Nitrophenyl)thio]- (1a) and N-[(2,4-dichlorophenyl)thio)]-2,6-diphenyl-4-(3-pyridyl)phenylaminyl (1b), N-[(4-nitrophenyl)thio]- (2a) and N-[(2,4-dichlorophenyl)thio]-4-phenyl-2,6-di(3-pyridyl)phenylaminyl (2b) were generated by PbO2 oxidation of the corresponding precursors and isolated as radical crystals. For 1b X-ray crystallographic analysis was performed. The magnetic susceptibility measurements were carried out for the isolated radicals using a SQUID magnetometer in the temperature range 1.8 − 300 K. The susceptibilities of 1a and 2a were analyzed in terms of a one-dimensional (1D) antiferromagnetic (AFM) regular Heisenberg model with exchange interaction of 2J/k B= −63.4 and −17.8 K, respectively, and that of 1b was interpreted in terms of a 1D AFM alternating Heisenberg model with 2J/k B = −12.8 K and α = 0.91. On the other hand, that of 2b was explained in terms of a 1D ferromagnetic regular Heisenberg model with 2J/k B = 22.4 K.

One-dimensional magnetism and the phase transition in

A crystal of was grown, which has a structure containing V-O-V-O linear chains along the c-axis. There a vanadium ion carries a spin of per ion. The magnetic susceptibility was measured in the region from 2 to 300 K up to 55 kG. The temperature dependence shows a broad maximum around 100 K. This is a characteristic of a 1D antiferromagnet. Fitting to the uniform 1D Heisenberg model is very good in the higher temperature region. This suggests the onset of antiferromagnetic order around 100 K. At 34 K, however, shows a kink followed by a ferromagnetic hump at lower temperature. This suggests some magnetic phase transition. At 2 K a slight hysteresis was observed in the magnetic field dependence. The above behaviour was interpreted as the process of transfer from 1D to weak 3D interaction, according to lowering temperature. Lattice parameters increased with decreasing temperature below 100 K, then showed a hump around 30 K. This anomalous behaviour corresponds to the above magnetic results. It has been concluded that is a one-dimensional antiferromagnet. We also suggest the existence of a weak ferromagnetic ordered state such as canted or ferri-magnetism by the V-O pairs in the lower temperature region.

Magnetic Raman Scattering from 1D Antiferromagnets.

We study Raman scattering from 1D antiferromagnets within the Fleury-Loudon scheme by applying a finite temperature Lanczos method to a 1D spin-half Heisenberg model with nearest-neighbor (J(1)) and second-neighbor (J(2)) interactions. The low-temperature spectra are analyzed in terms of the known elementary excitations of the system for J(2) = 0 and J(2) = 1/2. We find that the low-T Raman spectra are very broad for \J(2)/J(1) less than or equal to 0.3. This broad peak gradually diminishes and shifts with temperature, so that at T > J(1) the spectra are narrower and peaked at low frequencies. The experimental spectra for CuGeO3 are discussed in light of our calculations.

Experimental studies of one-dimensional quantum spin systems

We review the experimental results on a spin (S) one, one-dimensional Heisenberg antiferromagnet (1DHA). In particular, how has the existence of the Haldane gap been confirmed and what is the nature of the ground state, are discussed. In the latter part of this paper, our recent experiments on S = 2 1DHA and 1D antiferromagnets with competing exchange interactions are reported.

Exact solution to a strongly coupled Hubbard model in one dimension for high-Tc superconductors.

A Hamiltonian for the motion of oxygen holes strongly coupled to the Cu spins in a one-dimensional (1D) Cu-O lattice is solved exactly for all dopings. This Hamiltonian retains the dominant O-hole hopping term, that is, spin-exchange hopping of the hole spin with the intervening Cu spin and neglects the weaker non-spin-exchange hopping term. The excitations naturally separate into two independent quasiparticles: spinons and holons. It is this Hamiltonian that should be taken as the correct zeroth-order Hamiltonian from which perturbation theory should be applied. We show that the spinon spectrum is the spectrum of the 1D antiferromagnet incommensurate with the Cu lattice and the holons are spinless noninteracting fermions in a cosine band. The Cu-Cu spin correlation in the ground state increases linearly with doping from antiferromagnetic (-0.443) at x=0 to ferromagnetic (\ensuremath{\approxeq}0.19) at x=1.

Temperature dependence of hot magnon sidebands in antiferromagnets

The temperature dependence of the absorption intensity of hot magnon sidebands is investigated for the two-dimensional (2D) antiferromagnet BaMnF 4, and the 3D antiferromagnet MnF 2. A general expression for the temperature dependence is presented for 1D, 2D and 3D antiferromagnets.

Spectroscopic and magneto-optical properties of quasi 1D antiferromagnets AVX3 (A = Cs, Rb; X = Cl, Br, I)

Single crystal absorption and Zeeman experiments on the 4A2g → 2T2g transitions in CsVBr3 show evidence of both 1D and 3D magnetic ordering.