Finite-temperature order-disorder phase transition in a frustrated bilayer quantum Heisenberg antiferromagnet in strong magnetic fields

Johannes Richter, Oleg Derzhko, and Taras Krokhmalskii
Phys. Rev. B 74, 144430 – Published 27 October 2006

Abstract

We investigate the thermodynamic properties of the frustrated bilayer quantum Heisenberg antiferromagnet at low temperatures in the vicinity of the saturation magnetic field. The low-energy degrees of freedom of the spin model are mapped onto a hard-square gas on a square lattice. We use exact diagonalization data for finite spin systems to check the validity of such a description. Using a classical Monte Carlo method we give a quantitative description of the thermodynamics of the spin model at low temperatures around the saturation field. The main peculiarity of the considered two-dimensional Heisenberg antiferromagnet is related to a phase transition of the hard-square model on the square lattice, which belongs to the two-dimensional Ising model universality class. It manifests itself in a logarithmic (low-) temperature singularity of the specific heat of the spin system observed for magnetic fields just below the saturation field.

    • Received 30 June 2006

    DOI:https://doi.org/10.1103/PhysRevB.74.144430

    ©2006 American Physical Society

    Authors & Affiliations

    Johannes Richter1, Oleg Derzhko1,2,3, and Taras Krokhmalskii2

    • 1Institut für Theoretische Physik, Universität Magdeburg, P.O. Box 4120, D-39016 Magdeburg, Germany
    • 2Institute for Condensed Matter Physics, National Academy of Sciences of Ukraine, 1 Svientsitskii Street, L’viv-11, 79011, Ukraine
    • 3National University “Lvivska Politechnika,” 12 S. Bandera Street, L’viv, 79013, Ukraine

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    Issue

    Vol. 74, Iss. 14 — 1 October 2006

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