Jozef Strecka

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. 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.

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

Ground-state and finite-temperature properties of the mixed spin- 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 rigorous evidence for quantized plateaux 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.

Generalized algebraic transformations and exactly solvable classical-quantum models ☆

The rigorous approach aimed at providing exact analytical results for hybrid classical-quantum models is elaborated on the grounds of generalized algebraic mapping transformations. This conceptually simple method allows one to obtain novel interesting exact results for the hybrid classical-quantum models, which may for instance describe interacting many-particle systems composed of the classical Ising spins and quantum Heisenberg spins, the localized Ising spins and delocalized electrons, or many other hybrid systems of a mixed classical-quantum nature.

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 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.

Existence of a 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 phase 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 Heisenberg interaction parameters, as well as on the strength of the XXZ Heisenberg exchange anisotropy.

Thermodynamic properties of a tetramer Ising-Heisenberg bond-alternating chain as a model system for Cu(3-Chloropyridine)2(N3)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)

Reentrant phase transitions and multicompensation points in the mixed-spin Ising ferrimagnet on a decorated Bethe lattice

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

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Mixed spin-1/2 and spin-1 Ising model with uniaxial and biaxial single-ion anisotropy on the Bethe lattice

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Exact solution of the geometrically frustrated spin-1/2 Ising-Heisenberg model on the triangulated Kagome (triangles-in-triangles) lattice

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