80 research outputs found
Electron Spin Resonance in a Spin-1/2 Heisenberg Strong-rung Ladder
Cu(CHN)Cl, a strong-rung spin-1/2 Heisenberg ladder compound,
is probed by means of electron spin resonance (ESR) spectroscopy in the
field-induced gapless phase above . The temperature dependence of the
ESR linewidth is analyzed in the quantum field theory framework, suggesting
that the anisotropy of magnetic interactions plays a crucial role, determining
the peculiar low-temperature ESR linewidth behavior. In particular, it is
argued that the uniform Dzyaloshinskii-Moriya interaction (which is allowed on
the bonds along the ladder legs) can be the source of this behavior in
Cu(CHN)Cl
Magnetization plateaux cascade in the frustrated quantum antiferromagnet CsCoBr
We have found an unusual competition of two frustration mechanisms in the 2D
quantum antiferromagnet CsCoBr. The key actors are the alternation of
single-ion planar anisotropy direction of the individual magnetic Co
ions, and their arrangement in a distorted triangular lattice structure. In
particular, the uniquely oriented Ising-type anisotropy emerges from the
competition of easy-plane ones, and for a magnetic field applied along this
axis one finds a cascade of five ordered phases at low temperatures. Two of
these phases feature magnetization plateaux. The low-field one is supposed to
be a consequence of a collinear ground state stabilized by the anisotropy,
while the other plateau bears characteristics of an "up-up-down" state
exclusive for lattices with triangular exchange patterns. Such coexistence of
the magnetization plateaux is a fingerprint of competition between the
anisotropy and the geometric frustration in CsCoBr.Comment: 10 pages, 8 figure
Modes of magnetic resonance in the spin liquid phase of Cs2CuCl4
We report the observation of a frequency shift and splitting of the electron
spin resonance (ESR) mode of the low-dimensional S=1/2 frustrated
antiferromagnet Cs2CuCl4 in the spin-correlated state below the Curie-Weiss
temperature 4 K but above the ordering temperature 0.62 K. The shift and
splitting exhibit strong anisotropy with respect to the direction of the
applied magnetic field and do not vanish in zero field. The low-temperature
evolution of spin resonance response is a result of the specific modification
of one-dimensional spinon continuum under the action of the uniform
Dzyaloshinskii-Moriya interaction (DM) within the spin chains. Parameters of
the uniform DM interaction are derived from the experiment.Comment: 10 pages, 12 figure
Confinement of fractional excitations in a triangular lattice antiferromagnet
High-resolution neutron and THz spectroscopies are used to study the magnetic
excitation spectrum of CsCoBr, a distorted-triangular-lattice
antiferromagnet with nearly XY-type anisotropy. What was previously thought of
as a broad excitation continuum [Phys. Rev. Lett. 129, 087201 (2022)] is shown
to be a series of dispersive bound states reminiscent of "Zeeman ladders" in
quasi-one-dimensional Ising systems. At wave vectors where inter-chain
interactions cancel at the Mean Field level, they can indeed be interpreted as
bound finite-width kinks in individual chains. Elsewhere in the Brillouin zone
their true two-dimensional structure and propagation are revealed.Comment: 11 pages, 8 figure
TG study of the Li[0.4]Fe[2.4]Zn[0.2]O[4] ferrite synthesis
In this paper, the kinetic analysis of Li-Zn ferrite synthesis was studied using thermogravimetry (TG) method through the simultaneous application of non-linear regression to several measurements run at different heating rates (multivariate non-linear regression). Using TG-curves obtained for the four heating rates and Netzsch Thermokinetics software package, the kinetic models with minimal adjustable parameters were selected to quantitatively describe the reaction of Li-Zn ferrite synthesis. It was shown that the experimental TG-curves clearly suggest a two-step process for the ferrite synthesis and therefore a model-fitting kinetic analysis based on multivariate non-linear regressions was conducted. The complex reaction was described by a two-step reaction scheme consisting of sequential reaction steps. It is established that the best results were obtained using the Yander three-dimensional diffusion model at the first stage and Ginstling-Bronstein model at the second step. The kinetic parameters for lithium-zinc ferrite synthesis reaction were found and discussed
Intramolecular Imino Diels−Alder Reaction: Progress toward the Synthesis of Uncialamycin
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