Quantum phase transitions in alternating spin-(1/2, 5/2) Heisenberg chains |
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Authors: | Tenório Ant?nio S F Montenegro-Filho R R Coutinho-Filho M D |
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Institution: | Laboratório de Física Teórica e Computacional, Departamento de Física, Universidade Federal de Pernambuco, CEP 50670-901, Recife, Pernambuco, Brazil. |
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Abstract: | The ground state spin-wave excitations and thermodynamic properties of two types of ferrimagnetic chains are investigated: the alternating spin-1/2 spin-5/2 chain and a similar chain with a spin-1/2 pendant attached to the spin-5/2 site. Results for magnetic susceptibility, magnetization and specific heat are obtained through the finite-temperature Lanczos method with the aim of describing the available experimental data, as well as comparison with theoretical results from the semiclassical approximation and the low-temperature susceptibility expansion derived from Takahashi's modified spin-wave theory. In particular, we study in detail the temperature versus magnetic field phase diagram of the spin-1/2 spin-5/2 chain, in which several low-temperature quantum phases are identified: the Luttinger liquid phase, the ferrimagnetic plateau and the fully polarized phase, and the respective quantum critical points and crossover lines. |
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