Specific heat and structure factor in the square ANNNI model by Monte Carlo simulation

E. Rastelli, S. Regina, and A. Tassi
Phys. Rev. B 81, 094425 – Published 25 March 2010

Abstract

The axial (or anisotropic) next-nearest-neighbor Ising (ANNNI) model has been widely investigated: exact solution exists in one dimension; analytic and numerical treatments in two, and three dimensions suggest a rich phase diagram. Some controversial results obtained especially by Monte Carlo (MC) simulations are discussed. We conclude that in the region of weak competition (κ=J2/J1<1/2) the size scaling analysis is the same as that obtained in the nearest-neighbor (NN) Ising model. For κ>1/2 we find a series of very sharp peaks in the specific heat due to the discreteness of the lattice. The structure factor supports and explains the existence of the specific heat peaks. Very long simulations have been performed (107 and 108 MC steps per spin) because the relaxation time is huge for such a frustrated system. A careful comparison of MC simulations for different lattice sizes suggests that the Kosterlitz-Thouless phase is present for all κ>1/2.

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  • Received 4 December 2009

DOI:https://doi.org/10.1103/PhysRevB.81.094425

©2010 American Physical Society

Authors & Affiliations

E. Rastelli*, S. Regina, and A. Tassi

  • Dipartimento di Fisica dell’Università, Parco Area delle Scienze 7/A, 43100 Parma, Italy

  • *Present address: Istituto IMEM of CNR, Parco Area delle Scienze, 43100 Parma, Italy; rastelli@fis.unipr.it

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Vol. 81, Iss. 9 — 1 March 2010

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