Critical temperature and low-energy excitations in gapped spin systems with defects
| Autor: | Timkovskii, F. D., Syromyatnikov, A. V. |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 103, 024420 (2021) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.103.024420 |
| Popis: | We discuss theoretically the magnetically ordered phase induced by magnetic and nonmagnetic impurities in three-dimensional and quasi-low-dimensional systems with singlet ground states separated by a gap from excited triplet states. Using ideas of the percolation theory, we estimate the transition temperature $T_N(n)$ to the N\'eel phase at a small concentration $n$ of defects, derive the density of states of low-energy elementary excitations, and examine the contribution of these excitations to the specific heat and magnetization. Our expressions for $T_N(n)$ and for the specific heat describe well available experimental findings obtained in various appropriate systems: spin-$\frac12$ dimer materials, spin-ladder compounds, spin-Peierls and Haldane chain materials. However, our expression for $T_N(n)$ differs considerably from many of those proposed before. Comment: 9 pages, 2 figures, 1 table |
| Databáze: | arXiv |
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