arXiv subjects

Jozef Strecka

Publications and source records attributed to Jozef Strecka.

123 records · Page 7Linked to original sources

arXiv2006

Disordered and ordered states of exactly solvable Ising-Heisenberg planar models with a spatial anisotropy

Ground-state and finite-temperature properties of a special class of exactly solvable Ising-Heisenberg planar models are examined using the generalized decoration-iteration and star-triangle mapping transformations. The investigated spin systems exhibit an interesting quantum behaviour manifested in a remarkable geometric spin frustration, which appears notwithstanding the purely ferromagnetic interactions of the considered model systems. This kind of spin frustration originates from an easy-plane anisotropy in the XXZ Heisenberg interaction between nearest-neighbouring spins that favours ferromagnetic ordering of their transverse components, whereas their longitudinal components are aligned antiferomagnetically.

cond-mat.dis-nn↗

arXiv2006

Magnetic properties of a mixed spin-1/2 and spin-3/2 Ising model with an uniaxial and biaxial crystal-field potential

Magnetic properties of a mixed spin-1/2 and spin-3/2 Ising model on honeycomb lattice are investigated within the framework of an exact star-triangle mapping transformation. The particular attention is focused on the effect of uniaxial and biaxial crystal-field potentials that basically influence the magnetic behaviour of the spin-3/2 atoms. Our results for the basic thermodynamic quantities, as well as the dynamical time-dependent autocorrelation function indicate the spin tunneling between the $| \pm \frac32>$ and $| \mp \frac12>$ states in two different magnetically ordered phases OP$_1$ and OP$_2$, respectively.

cond-mat.stat-mech↗

arXiv2006

Exact results of a mixed spin-1/2 and spin-S Ising model on a bathroom tile (4-8) lattice: effect of uniaxial single-ion anisotropy

Effect of uniaxial single-ion anisotropy upon magnetic properties of a mixed spin-1/2 and spin-S (S>=1) Ising model on a bathroom tile (4-8) lattice is examined within the framework of an exact star-triangle mapping transformation. The particular attention is focused on the phase diagrams established for several values of the quantum spin number S. It is shown that the mixed-spin bathroom tile lattice exhibits very similar phase boundaries as the mixed-spin honeycomb lattice whose critical points are merely slightly enhanced with respect to the former ones. The influence of uniaxial single-ion anisotropy upon the total magnetization vs. temperature dependence is particularly investigated as well.

cond-mat.stat-mech↗

arXiv2006

Exact solution of the spin-1/2 Ising model on the Shastry-Sutherland (orthogonal-dimer) lattice

A star-triangle mapping transformation is used to establish an exact correspondence between the spin-1/2 Ising model on the Shastry-Sutherland (orthogonal-dimer) lattice and respectively, the spin-1/2 Ising model on a bathroom tile (4-8) lattice. Exact results for the critical temperature and spontaneous magnetization are obtained and compared with corresponding results on the regular Ising lattices.

cond-mat.stat-mech↗

arXiv2006

Geometric frustration in the class of exactly solvable Ising-Heisenberg diamond chains

Ground-state and finite-temperature properties of the mixed spin-1/2 and spin-S Ising-Heisenberg diamond chains are examined within an exact analytical approach based on the generalized decoration-iteration map. A particular emphasis is laid on the investigation of the effect of geometric frustration, which is generated by the competition between Heisenberg- and Ising-type exchange interactions. It is found that an interplay between the geometric frustration and quantum effects gives rise to several quantum ground states with entangled spin states in addition to some semi-classically ordered ones. Among the most interesting results to emerge from our study one could mention a rigorous evidence for quantized plateux in magnetization curves, an appearance of the round minimum in the thermal dependence of susceptibility times temperature data, double-peak zero-field specific heat curves, or an enhanced magnetocaloric effect when the frustration comes into play. The triple-peak specific heat curve is also detected when applying small external field to the system driven by the frustration into the disordered state.

cond-mat.stat-mech↗

arXiv2005

Thermodynamic properties of a tetramer ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain as a model system for Cu(3-Clpy)$_2$(N$_3$)$_2$

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)$_2$(N$_3$)$_2$ (3-Clpy=3-Chloropyridine).

cond-mat.mtrl-sci↗

arXiv2004

Effect of uniaxial and biaxial crystal-field potential on magnetic properties of a mixed spin-1/2 and spin-1 Ising model on honeycomb lattice

Magnetic properties of a mixed spin-1/2 and spin-1 Ising model on honeycomb lattice are exactly investigated within the framework of generalized star-triangle mapping transformation. The particular attention is focused on the effect of uniaxial and biaxial crystal-field anisotropies that basically influence the magnetic behaviour of the spin-1 atoms. Our results for the basic thermodynamic quantities, as well as the dynamical time-dependent autocorrelation function indicate the spin tunneling between the $| +1>$ and $| - 1>$ states in the magnetically ordered phase.

cond-mat.stat-mech↗

arXiv2003

Existence of the magnetization plateau in a class of exactly solvable Ising-Heisenberg chains

The mapping transformation technique is applied to obtain exact results for the spin-1/2 and spin-S (S=1/2,1) Ising-Heisenberg antiferromagnetic chain in the presence of an external magnetic field. Within this scheme, a field-induced first-order metamagnetic transition resulting in multiplateau magnetization curves, is investigated in detail. It is found that the scenario of the plateau formation depends fundamentally on the ratio between Ising and Heisenbrg interaction constants, as well as on the anisotropy strength of the XXZ Heisenberg interaction.

cond-mat.stat-mech↗

arXiv2003

On the Ising-Heisenberg model with the doubly decorated network structure I

Using an exact mapping transformation method, magnetic properties of a spin-1/2 and spin-1 doubly decorated Ising-Heisenberg model are investigated in detail. By assuming that both interaction parameters are ferromagnetic, we found in addition to an usual ferromagnetic phase another two phases with a nontrivial long-range order.

cond-mat.stat-mech↗

arXiv2003

Spin Frustration in an Exactly Solvable Ising-Heisenberg Diamond Chain

Exact results of a mixed spin-1/2 and spin-1 Ising-Heisenberg diamond chain are obtained applying a generalized decoration-iteration transformation. Depending on the values of external field, exchange parameters and anisotropy, there exist six different phases in the ground state of the system. The magnetic order of these phases is briefly described in this work.

cond-mat.stat-mech↗

arXiv2002

Magnetic properties of exactly solvable doubly decorated Ising-Heisenberg planar models

Applying the decoration-iteration procedure, we introduce a class of exactly solvable doubly decorated planar models consisting both of the Ising- and Heisenberg-type atoms. Exact solutions for the ground state, phase diagrams and basic physical quantities are derived and discussed. The detailed analysis of the relevant quantities suggests the existence of an interesting quantum antiferromagnetic phase in the system.

cond-mat.stat-mech↗

arXiv2002

Exact results of the one-dimensional tranverse Ising model in an external longitudinal magnetic field

Magnetic properties of the 1D mixed spin-1/2 and spin-S (S >1/2) transverse Ising model in the presence of an external longitudinal magnetic field are calculated exactly by the use of the generalised decoration-iteration mapping transformation. By assuming that only the spin-S atoms do interact with the transverse field the exact results for the Gibbs free energy, longitudinal magnetization, transverse magnetization, entropy and specific heat have been derived and discussed in detail. In addition to the standard temperature variations of the transverse magnetization, another two non-trivial thermal dependences have been found. The results support the concept that the spin reorientation from the longitudinal towards the transverse field direction takes place in the narrow temperature region.

cond-mat.stat-mech↗

arXiv2002

Influence of an Anisotropic Crystalline Field on the Magnetic Properties of a Mixed Spin-1/2 and Spin-1 Ising Model

The mixed spin-1/2 and spin-1 Ising model in the presence of an anisotropic crystalline field is treated exactly within the framework of an extended star-triangle mapping transformation. The exact results for the phase diagrams, magnetization, internal energy and specific heat are derived and discussed in detail. The relevant mapping suggests that an isotropic in-plane crystal field (D^x = D^y) leads to the same effects as the hard-axis crystal field (D^z), whereas the in-plane anisotropy (D^x \neq D^y) is responsible also for the randomization of the magnetic ordering (transverse-field like effect).

cond-mat.stat-mech↗

arXiv2002

Existence of a New Quantum Phase in Exactly Solvable Antiferromagnetic Ising-Heisenberg Models on Planar Lattices

In this work we deal with doubly decorated Ising-Heisenberg models on planar lattices. Applying the generalized decoration-iteration transformation we obtain exact results for the antiferromagnetic version of the model. The existence of a new quantum dimerized phase is predicted and its physical properties are studied and analyzed. Particular attention has been paid to the investigation of the phase boundaries, pair-correlation functions and specific heat. A possible application of the present work to some molecular magnets is also drawn.

cond-mat.stat-mech↗

arXiv2002

Thermodynamic properties of the exactly solvable transverse Ising model on decorated planar lattices

The generalized mapping transformation technique is used to obtain the exact solution for the transverse Ising model on decorated planar lattices. Within this scheme, the basic thermodynamic quantities are calculated for different planar lattices with arbitrary spins of decorating atoms. The particular attention has been paid to the investigation of the transverse-field effects on magnetic properties of the system under investigation. The most interesting numerical results for the phase diagrams, compensation temperatures and several thermodynamic quantities are discussed in detail for the ferrimagnetic version of the model.

cond-mat.stat-mech↗