Phase Transitions in a Coupled Electron and Spin Model on the Shastry-Sutherland Lattice |
| P. Farkašovský, H. Čenčariková
Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice, Slovakia |
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| The thermodynamics of a simple electron-spin model proposed recently for a description of magnetization processes in rare-earth tetraborides is studied numerically by the canonical Monte Carlo method in two-dimensions. The model is based on the coexistence of two subsystems, and namely, the spin subsystem described by the Ising model and the electronic subsystem described by the free-electron model on the Shastry-Sutherland lattice (SSL). Moreover, both subsystems are coupled by the anisotropic spin-dependent interaction of the Ising type. At T=0 the system exhibits the magnetization plateau (MP) at m/ms=1/2, 1/3, 1/5, 1/7, 1/9 and 1/11 of the saturated spin magnetization ms. For the largest phases corresponding to m/ms=0, 1/3 and 1/2 we have examined the nature of the phase transitions from the low-temperature ordered phase (LTOP) to the high-temperature disordered phase (HTDP). It is shown that all phases persist also at finite temperatures (up to the critical temperature Tc) and that the phase transition at the critical point is of the second order for the m/ms=0 phase and of the first order for the m/ms=1/3 and 1/2 phases. |
DOI: 10.12693/APhysPolA.126.44 PACS numbers: 75.10.-b, 75.40.Mg, 05.70.Fh |