Framework Of Classical Heisenberg Model Research Articles

Multiferroicity in Perovskite Manganite Superlattice**Supported by the National Natural Science Foundation of China (NSFC) under Grant No. 11447136

Multiferroic properties of short period perovskite type manganite superlattice ((R1MnO3)n/(R2MnO3)n (n=1,2,3)) are considered within the framework of classical Heisenberg model using Monte Carlo simulation. Our result revealed the interesting behaviors in Mn spins structure in superlattice. Apart from simple plane spin cycloid structure which is shown in all manganites including bulk, film, and superlattice here in low temperature, a non-coplanar spiral spin structure is exhibited in a certain temperature range when n equals 1, 2 or 3. Specific heat, spin-helicity vector, spin correlation function, spin-helicity correlation function, and spin configuration are calculated to confirm this non-coplanar spiral spin structure. These results are associated with the competition among exchange interaction, magnetic anisotropy, and Dzyaloshinskii-Moriya interaction.

Coexistence of two cycloid-phases in multiferroic RMnO3: Consequence of the next-nearest-neighbor spin interaction modulations

The modulation of the next-nearest-neighbor spin interaction in RMnO3-type manganites is considered and its effect on the multiferroic behaviors is investigated within the framework of classical Heisenberg model using Monte Carlo simulation. Two types of the modulations, i.e., the symmetric perturbations in which the interactions over the lattice are symmetrically modulated with an equal distribution to maintain the mean interaction invariant and the asymmetric perturbations in which the interactions over the lattice are randomly modulated with variable mean interaction, are taken into account. It is shown that both the types of modulations can drive the reorientation of the spiral spin order and thus lead to the coexistence of two cycloid-phases within appropriate magnitudes of modulation. The two multiferroic phase coexistence can be understood as the consequence of the competition between the single-ion anisotropy and the Dzyaloshinskii-Mariya interaction. A comparison of the simulated results with recent relevant experiments on multiferroic manganites is also presented.

Monte Carlo simulation of anisotropic Shastry–Sutherland lattice in the framework of classical Heisenberg model multiferroic

Monte Carlo simulation of two-dimensional Shastry–Sutherland lattice has been carried out using heat-bath method. The dependencies of magnetization M on external field H have been obtained in the framework of classical Heisenberg model. In certain interval of exchange parameters ratio the plateau of magnetization corresponding to M = 1/3 has been observed. The influence of exchange anisotropy of “easy-axis” type on this plateau width is studied. It has been shown that even weak anisotropy (∼1−2%) leads to essential enlargement of the plateau. The dependence of critical temperature on exchange parameters ratio has been established.

Nonmagnetic B-site substitution induced two-phase coexistence in multiferroic manganites: Monte Carlo simulation

The influence of B-site nonmagnetic substitution on the spiral spin ordering in multiferroic manganites is investigated by Monte Carlo simulation within the framework of classical Heisenberg model. It is revealed that the nonmagnetic substitution significantly suppressed the multiferroic phase transitions, consistent with experimental results. The boundary between ab-cycloidal phase and bc-cycloidal phase in the temperature-substitution phase diagram becomes faint gradually with increasing substitution level. A coexistence of two cycloidal spin phases is identified when the substitution level surpassed a threshold. The physical origin for the two-phase coexistence induced by the nonmagnetic B-site substitution is discussed.