In-chain Interaction Research Articles

Antiferromagnetic and ferromagnetic spintronics and the role of in-chain and inter-chain interaction on spin transport in the Heisenberg ferromagnet

Spin-transport and current-induced torques in ferromagnet heterostructures given by a ferromagnetic domain wall are investigated. Furthermore, the continuum spin conductivity is studied in a frustrated spin system given by the Heisenberg model with ferromagnetic in-chain interaction J_1<0 between nearest neighbors and antiferromagnetic next-nearest-neighbor in-chain interaction J_2>0 with aim to investigate the effect of the phase diagram of the critical ion single anisotropy D_c as a function of J_2 on conductivity. We consider the model with the moderate strength of the frustrating parameter such that in-chain spin-spin correlations that are predominantly ferromagnetic. In addition, we consider two inter-chain couplings J_{perp ,y} and J_{perp ,z}, corresponding to the two axes perpendicular to chain where ferromagnetic as well as antiferromagnetic interactions are taken into account.

Density-density propagator for one-dimensional interacting spinless fermions with nonlinear dispersion and calculation of the Coulomb drag resistivity

Using bosonization-fermionization transformation, we map the Tomonaga-Luttinger model of spinless fermions with nonlinear dispersion on the model of fermionic quasiparticles whose interaction is irrelevant in the renormalization group sense. Such mapping allows us to set up an expansion for the density-density propagator of the original Tomonaga-Luttinger Hamiltonian in orders of the (irrelevant) quasiparticle interaction. The lowest order term in such an expansion is proportional to the propagator for free fermions. The next term is also evaluated. The propagator found is used for calculation of the Coulomb drug resistivity $r$ in a system of two capacitively coupled one-dimensional conductors. It is shown that $r$ is proportional to ${T}^{2}$ for both free and interacting fermions. The marginal repulsive in-chain interaction acts to reduce $r$ as compared to the noninteracting result. The correction to $r$ due to the quasiparticle interaction is found as well. It scales as ${T}^{4}$ at low temperature.

Electronic structure and magnetic properties of Bi2CuO4

Bi2CuO4 is a spin 1/2 model compound with ferromagnetically (FM) ordered chains that are antiferromagnetically (AFM) arranged with respect to each other. To investigate the microscopic origin of this unusual magnetic structure, we performed DFT calculations to evaluate the relevant orbitals and couplings. Total energy calculations yield a magnetic ground state in agreement with the experimental data. Based on a tight-binding fit we estimated the leading exchange integrals. The main coupling arises between the chains, while the in-chain interaction is relatively small. The FM arrangement of chains is due to strong AFM exchange of neighbouring CuO4 units of the different chains.

Variational description of the dimensional crossover in an array of coupled one-dimensional conductors

Variational wave function is proposed to describe electronic properties of an array of one-dimensional conductors coupled by transverse hopping and interaction. For weak or intermediate in-chain interaction the wave function has the following structure: Tomonaga-Luttinger bosons with momentum higher then some variational quantity \tilde\Lambda are in their ground state while other bosons (with |k|<\tilde\Lambda) form kinks -- fermion-like excitations of the Tomonaga-Luttinger boson field. Nature of the ground state for this quasiparticles can be determined by solving three dimensional effective hamiltonian. Since the anisotropy of the effective hamiltonian is small the use of the mean field theory is justified. For repulsive interaction possible phases are density wave and p-wave superconductivity. Our method allows us to calculate the low-energy part of different electronic Green's functions. In order to do that it is enough to apply standard perturbation theory technique to the effective hamiltonian. When the in-chain interaction is strong \tilde\Lambda vanishes and no fermionic excitation is present in the system. In this regime the dynamics is described by transversally coupled Tomonaga-Luttinger bosons.

Zone-boundary excitations in coupled Haldane spin chain compoundsPbNi2V2O8andSrNi2V2O8

Magnetic excitations in the quasi-one-dimensional quantum antiferromagnets ${\mathrm{PbNi}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ and ${\mathrm{SrNi}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ are measured all the way up to the zone-boundary energy using inelastic neutron scattering from powder samples. An estimate for next-nearest-neighbor in-chain interactions is obtained. The role played by these interactions in spin-vacancy-induced magnetic ordering in ${\mathrm{PbNi}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ is discussed.

Ferromagnetism in 1d and 2d triangular nickel(II) -based compounds

We discuss in this paper the structure and magnetic properties of the one- and two-dimensional nickel(II) hydroxynitrates, Ni(OH)(NO3)H2O and Ni2(OH)2+x(NO3)2−x (x = 0.64, 0.74, 1.14), respectively. The former is described as a new double-chain system with two Heisenberg in-chain interactions between S = 1 spins, and a zero-field splitting contribution arising from single-ion anisotropy. From numerical computations up to 10 spin units, the exchange interactions of both systems are shown to be ferromagnetic, i.e. J1 = +26.9 K, and J2 = +6.9 K, with g = 2.22, and D = +1.76 K. At very low temperature, the magnetization and neutron diffraction data indicate the occurrence of long-range antiferromagnetic order with a metamagnetic transition for Hc = 0.25 T. The non-stoichiometric layered compounds Ni2(OH)2+x(NO3)2−x show the signature of 2d ferromagnetism, as demonstrated for the hydroxide parent compound Ni(OH)2. From a comparison of these lamellar derivatives, it appears that the increase in the interlayer distance when (OH)− is substituted by (NO3)−, associated with turbostratic disorder, strongly affects the 3d long-range order. Indeed, whereas Ni(OH)2 is a metamagnet with TN = 25.8 K, Ni2(OH)2+x(NO3)2−x exhibits a spin-glass-like behavior below 10 K.

Scaling properties of the two-chain model

Scaling properties of a self-dual field-theoretical model, describing two weakly coupled spinless Luttinger chains, are studied. A crossover to a sine-Gordon massive phase, with strongly developed two-particle interchain correlations, is described. It is argued that, in a wide range of the in-chain interaction, renormalization of the interchain hopping amplitude is determined by the Luttinger liquid effects.