Torrico Jordana, Strečka Jozef, Rojas Onofre, de Souza Sergio Martins, Lyra Marcelo Leite
Departamento de Física, Universidade Federal de Lavras, 37200-000 Lavras, Minas Gerais, Brazil.
Department of Theoretical Physics and Astrophysics, Faculty of Science, P. J. Šafárik University, 040 01 Košice, Slovak Republic.
Phys Rev E. 2020 Mar;101(3-1):032104. doi: 10.1103/PhysRevE.101.032104.
Phase transitions, compensation phenomenon, and magnetization of a ferroferrimagnetic ternary alloy AB_{ρ}C_{1-ρ} composed of three different kinds of magnetic ions A, B, and C with the spin magnitudes 1/2, 1, and 3/2 are examined within the framework of a mixed-spin Ising model on a honeycomb lattice with a selective annealed site disorder on one of its two sublattices. It is supposed that the first sublattice of a bipartite honeycomb lattice is formed by the spin-1/2 magnetic ions, while the sites of the second sublattice are randomly occupied either by the spin-1 magnetic ions with a probability ρ or the spin-3/2 magnetic ions with a probability 1-ρ, both being subject to a uniaxial single-ion anisotropy. The model under investigation can be exactly mapped into an effective spin-1/2 Ising model on a triangular lattice through the generalized star-triangle transformation. For a specific concentration of the spin-1 (spin-3/2) magnetic ions, it is shown that the ferroferrimagnetic version of the studied model may display a compensation temperature at which the total magnetization vanishes below a critical temperature. The critical temperature strikingly may also become independent of the concentration of the randomly mixed spin-1 and spin-3/2 magnetic ions for a specific value of a uniaxial single-ion anisotropy. The spontaneous magnetic order may be notably restored at finite temperatures through the order-by-disorder mechanism above a disordered ground state, which results in an anomalous temperature dependence of the total magnetization with double reentrant phase transitions.
在具有选择性退火位点无序的蜂窝晶格上的混合自旋伊辛模型框架内，研究了由三种不同自旋大小分别为1/2、1和3/2的磁性离子A、B和C组成的亚铁磁三元合金ABₚC₁₋ₚ的相变、补偿现象和磁化。假设二分蜂窝晶格的第一个子晶格由自旋为1/2的磁性离子形成，而第二个子晶格的位点以概率ρ被自旋为1的磁性离子随机占据，或以概率1 - ρ被自旋为3/2的磁性离子随机占据，两者都受到单轴单离子各向异性的影响。通过广义星 - 三角变换，所研究的模型可以精确地映射到三角晶格上的有效自旋为1/2的伊辛模型。对于自旋为1（自旋为3/2）磁性离子的特定浓度，研究表明所研究模型的亚铁磁版本可能会出现一个补偿温度，在该温度以下，总磁化强度在临界温度以下消失。对于单轴单离子各向异性的特定值，临界温度显著地也可能变得与随机混合的自旋为1和自旋为3/2磁性离子的浓度无关。在高于无序基态的有限温度下，通过无序诱导有序机制，自发磁序可能会显著恢复，这导致总磁化强度具有异常的温度依赖性，并伴有双重再入相变。
