34 research outputs found
Multiple frustration-induced plateaus in a magnetization process of the mixed spin-1/2 and spin-3/2 Ising-Heisenberg diamond chain
Magnetization process of the mixed spin-1/2 and spin-3/2 Ising-Heisenberg
diamond chain is examined by combining three exact analytical techniques: Kambe
projection method, decoration-iteration transformation and transfer-matrix
method. Multiple frustration-induced plateaus in a magnetization process of
this geometrically frustrated system are found provided that a relative ratio
between the antiferromagnetic Heisenberg- and Ising-type interactions exceeds
some particular value. By contrast, there is just a single magnetization
plateau if the frustrating Heisenberg interaction is sufficiently small
compared to the Ising one.Comment: 4 pages, 1 figure, presented at International Conference on Highly
Frustrated Magnetism (HFM 2008), 7-12 September, 2008, Braunschweig, Germany,
to be published in Journal of Physics: Conference Serie
Exactly solvable mixed-spin Ising-Heisenberg diamond chain with the biquadratic interactions and single-ion anisotropy
An exactly solvable variant of mixed spin-(1/2,1) Ising-Heisenberg diamond
chain is considered. Vertical spin-1 dimers are taken as quantum ones with
Heisenberg bilinear and biquadratic interactions and with single-ion
anisotropy, while all interactions between spin-1 and spin-1/2 residing on the
intermediate sites are taken in the Ising form. The detailed analysis of the
ground state phase diagram is presented. The phase diagrams have shown to
be rather rich, demonstrating large variety of ground states: saturated one,
three ferrimagnetic with magnetization equal to 3/5 and another four
ferrimagnetic ground states with magnetization equal to 1/5. There are also two
frustrated macroscopically degenerated ground states which could exist at zero
magnetic filed.
Solving the model exactly within classical transfer-matrix formalism we
obtain an exact expressions for all thermodynamic function of the system. The
thermodynamic properties of the model have been described exactly by exact
calculation of partition function within the direct classical transfer-matrix
formalism, the entries of transfer matrix, in their turn, contain the
information about quantum states of vertical spin-1 XXZ dimer (eigenvalues of
local hamiltonian for vertical link).Comment: 14 pages, 9 figure
Spontaneous order in the highly frustrated spin-1/2 Ising-Heisenberg model on the triangulated Kagome lattice due to the Dzyaloshinskii-Moriya anisotropy
The spin-1/2 Ising-Heisenberg model on the triangulated Kagome
(triangles-in-triangles) lattice is exactly solved by establishing a precise
mapping correspondence to the simple spin-1/2 Ising model on Kagome lattice. It
is shown that the disordered spin liquid state, which otherwise occurs in the
ground state of this frustrated spin system on assumption that there is a
sufficiently strong antiferromagnetic intra-trimer interaction, is eliminated
from the ground state by arbitrary but non-zero Dzyaloshinskii-Moriya
anisotropy.Comment: 4 pages, 3 figures, to be presented at conference Highly Frustrated
Magnetism, 7-12 September 2008, Braunschweig, German
The square-kagome quantum Heisenberg antiferromagnet at high magnetic fields: The localized-magnon paradigm and beyond
We consider the spin-1/2 antiferromagnetic Heisenberg model on the
two-dimensional square-kagome lattice with almost dispersionless lowest magnon
band. For a general exchange coupling geometry we elaborate low-energy
effective Hamiltonians which emerge at high magnetic fields. The effective
model to describe the low-energy degrees of freedom of the initial frustrated
quantum spin model is the (unfrustrated) square-lattice spin-1/2 model in
a -aligned magnetic field. For the effective model we perform quantum Monte
Carlo simulations to discuss the low-temperature properties of the
square-kagome quantum Heisenberg antiferromagnet at high magnetic fields. We
pay special attention to a magnetic-field driven
Berezinskii-Kosterlitz-Thouless phase transition which occurs at low
temperatures.Comment: 6 figure
Spin-1/2 Ising-Heisenberg model with the pair XYZ Heisenberg interaction and quartic Ising interactions as the exactly soluble zero-field eight-vertex model
The spin-1/2 Ising-Heisenberg model with the pair XYZ Heisenberg interaction
and quartic Ising interactions is exactly solved by establishing a precise
mapping relationship with the corresponding zero-field (symmetric) eight-vertex
model. It is shown that the Ising-Heisenberg model with the ferromagnetic
Heisenberg interaction exhibits a striking critical behavior, which manifests
itself through re-entrant phase transitions as well as continuously varying
critical exponents. The changes of critical exponents are in accordance with
the weak universality hypothesis in spite of a peculiar singular behavior to
emerge at a quantum critical point of the infinite order, which occurs at the
isotropic limit of the Heisenberg interaction. On the other hand, the
Ising-Heisenberg model with the antiferromagnetic Heisenberg interaction
surprisingly exhibits less significant changes of both critical temperatures as
well as critical exponents upon varying a strength of the exchange anisotropy
in the Heisenberg interaction.Comment: 11 pages, 9 figure
Quantum phase transitions in the exactly solved spin-1/2 Heisenberg-Ising ladder
Ground-state behaviour of the frustrated quantum spin-1/2 two-leg ladder with
the Heisenberg intra-rung and Ising inter-rung interactions is examined in
detail. The investigated model is transformed to the quantum Ising chain with
composite spins in an effective transverse and longitudinal field by employing
either the bond-state representation or the unitary transformation. It is shown
that the ground state of the Heisenberg-Ising ladder can be descended from
three exactly solvable models: the quantum Ising chain in a transverse field,
the 'classical' Ising chain in a longitudinal field or the spin-chain model in
a staggered longitudinal-transverse field. The last model serves in evidence of
the staggered bond phase with alternating singlet and triplet bonds on the
rungs of two-leg ladder, which appears at moderate values of the external
magnetic field and consequently leads to a fractional plateau at a half of the
saturation magnetization. The ground-state phase diagram totally consists of
five ordered and one quantum disordered phase, which are separated from each
other either by the lines of discontinuous or continuous quantum phase
transitions. The order parameters are exactly calculated for all five ordered
phases and the quantum disordered phase is characterized through different
short-range spin-spin correlations.Comment: corrected version, figure A1 has been changed, accepted in J. Phys.
A, 19 pages, 7 figure
Magnetocaloric effect in spin-1/2 chains with three-spin interactions
We consider the exactly solvable spin-1/2 chain with the three-spin
interactions of the and types in an external (transverse)
magnetic field. We calculate the entropy and examine the magnetocaloric effect
for the quantum spin system. We discuss a relation between the cooling/heating
efficiency and the ground-state phase diagram of the quantum spin model. We
also compare ability to cool/heat in the vicinity of the quantum critical and
triple points. Moreover, we examine the magnetocaloric effect for the spin-1/2
chain with three-spin interactions in a random (Lorentzian) transverse
magnetic field.Comment: 10 pages, 8 figure
Thermodynamic properties of a tetramer ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain as a model system for Cu(3-Clpy)(N)
Thermodynamic properties of a tetramer
ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain
are investigated by the use of an exact mapping transformation technique. Exact
results for the magnetization, susceptibility and specific heat in the zero as
well as nonzero magnetic field are presented and discussed in detail. The
results obtained from the mapping are compared with the relevant experimental
data of Cu(3-Clpy)(N) (3-Clpy=3-Chloropyridine).Comment: 10 pages, 1 table, 14 figures, to be presented at CSMAG04 conferenc
Lattice distortions in a sawtooth chain with Heisenberg and Ising bonds
An exactly solvable model of the sawtooth chain with Ising and Heisenberg
bonds and with coupling to lattice distortion for Heisenberg bonds is
considered in the magnetic field. Using the direct transfer-matrix formalism an
exact description of the thermodynamic functions is obtained. The ground state
phase diagrams for all regions of parameters values containing phases
corresponding to the magnetization plateaus at and 1/2 have been
obtained. Exact formulas for bond distortions for various ground states are
presented. A novel mechanism of magnetization plateau stabilization
corresponding to state is reported.Comment: 16 pages, 12 figure
Magnetic properties of the quantum spin-1/2 XX diamond chain: The Jordan-Wigner approach
The Jordan-Wigner transformation is applied to study magnetic properties of
the quantum spin-1/2 model on the diamond chain. Generally, the
Hamiltonian of this quantum spin system can be represented in terms of spinless
fermions in the presence of a gauge field and different gauge-invariant ways of
assigning the spin-fermion transformation are considered. Additionally, we
analyze general properties of a free-fermion chain, where all gauge terms are
neglected and discuss their relevance for the quantum spin system. A
consideration of interaction terms in the fermionic Hamiltonian rests upon the
Hartree-Fock procedure after fixing the appropriate gauge. Finally, we discuss
the magnetic properties of this quantum spin model at zero as well as non-zero
temperatures and analyze the validity of the approximation used through a
comparison with the results of the exact diagonalization method for finite (up
to 36 spins) chains. Besides the plateau the most prominent feature of
the magnetization curve is a jump at intermediate field present for certain
values of the frustrating vertical bond.Comment: 12 pages, 9 figures, accepted for publication in Eur. Phys. J.