title: Quantum phase transitions in alternating spin-(1/2, 5/2) Heisenberg chains.
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.
authors: Laboratório de Física Teórica e Computacional, Departamento de Física, Universidade Federal de Pernambuco, CEP 50670-901, Recife, Pernambuco, Brazil.
authors: Antônio S F
authors: AS
authors: Tenório
authors: R R
authors: RR
authors: Montenegro-Filho
authors: M D
authors: MD
authors: Coutinho-Filho