Vadim Ohanyan

Exactly solvable mixed-spin Ising-Heisenberg diamond chain with 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

Exact calculation of the magnetocaloric effect in the spin- 1 2 X X Z chain

T=0

Exactly solvable Ising-Heisenberg chain with triangular XXZ-Heisenberg plaquettes

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).

Magnetization non-rational quasi-plateau and spatially modulated spin order in the model of the single-chain magnet, [{(CuL)2Dy}{Mo(CN)8}]·2CH3CN·H2O

We calculate the entropy and cooling rate of the antiferromagnetic spin-

Phase diagrams of the Ising-Heisenberg chain with S = 1/2 triangular XXZ clusters

\frac{1}{2}

Correlation functions in one-dimensional spin lattices with Ising and Heisenberg bonds

XXZ

Magnetocaloric effect in spin-1/2 XX chains with three-spin interactions

chain under an adiabatic demagnetization process using the quantum transfer-matrix technique and nonlinear integral equations. The limiting case of the Ising chain (corresponding to infinitely large anisotropy) is presented for comparison. Our exact results for the Heisenberg chain are used as a cross-check for the numerical exact diagonalization as well as quantum Monte Carlo simulations and allow us to benchmark the numerical methods. Close to field-induced quantum phase transitions we observe a large magnetocaloric effect. Furthermore, we verify universal low-temperature power laws in the cooling rate and entropy, in particular, linear scaling of entropy with temperature

Two-center quantum MICZ–Kepler system and the Zeeman effect in the charge–dyon system

T

Magnetism-driven ferroelectricity in spin-1/2

in the gapless Luttinger-liquid state and scaling as