Strečka Jozef, Karl'ová Katarína
Department of Theoretical Physics and Astrophysics, Faculty of Science, P. J. Šafárik University in Košice, Park Angelinum 9, 040 01 Košice, Slovakia.
Entropy (Basel). 2021 Nov 18;23(11):1533. doi: 10.3390/e23111533.
The magnetocaloric response of the mixed spin-1/2 and spin- (S>1/2) Ising model on a decorated square lattice is thoroughly examined in presence of the transverse magnetic field within the generalized decoration-iteration transformation, which provides an exact mapping relation with an effective spin-1/2 Ising model on a square lattice in a zero magnetic field. Temperature dependencies of the entropy and isothermal entropy change exhibit an outstanding singular behavior in a close neighborhood of temperature-driven continuous phase transitions, which can be additionally tuned by the applied transverse magnetic field. While temperature variations of the entropy display in proximity of the critical temperature Tc a striking energy-type singularity (T-Tc)log|T-Tc|, two analogous weak singularities can be encountered in the temperature dependence of the isothermal entropy change. The basic magnetocaloric measurement of the isothermal entropy change may accordingly afford the smoking gun evidence of continuous phase transitions. It is shown that the investigated model predominantly displays the conventional magnetocaloric effect with exception of a small range of moderate temperatures, which contrarily promotes the inverse magnetocaloric effect. It turns out that the temperature range inherent to the inverse magnetocaloric effect is gradually suppressed upon increasing of the spin magnitude .
在广义修饰-迭代变换中，研究了在横向磁场存在下，混合自旋-1/2和自旋-（S>1/2）伊辛模型在装饰正方形晶格上的磁热响应，该变换提供了与零磁场下正方形晶格上有效自旋-1/2伊辛模型的精确映射关系。熵和等温熵变的温度依赖性在温度驱动的连续相变的紧邻区域表现出显著的奇异行为，这可以通过施加的横向磁场进一步调节。虽然熵的温度变化在临界温度Tc附近表现出明显的能量型奇点（T-Tc）log|T-Tc|，但在等温熵变的温度依赖性中可以遇到两个类似的弱奇点。等温熵变的基本磁热测量因此可以提供连续相变的确凿证据。结果表明，除了一小范围的中等温度外，所研究的模型主要表现出传统的磁热效应，相反，这促进了逆磁热效应。结果表明，随着自旋大小的增加，逆磁热效应固有的温度范围逐渐受到抑制。
