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arXiv · 1305.2392

Phase transitions in the two-dimensional super-antiferromagnetic Ising model with next-nearest-neighbor interactions

A. saguia·B. Boechat·O. F. de Alcantara Bonfim·J. Florencio
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Abstract

We use Monte Carlo and Transfer Matrix methods in combination with extrapolation schemes to determine the phase diagram of the 2D super-antiferromagnetic (SAF) Ising model with next-nearest-neighbor (nnn) interactions in a magnetic field. The interactions between nearest-neighbor (nn) spins are ferromagnetic along x, and antiferromagnetic along y. We find that for sufficiently low temperatures and fields, there exists a region limited by a critical line of 2nd-order transitions separating a SAF phase from a magnetically induced paramagnetic phase. We did not find any region with either first-order transition or with re-entrant behavior. The nnn couplings produce either an expansion or a contraction of the SAF phase. Expansion occurs when the interactions are antiferromagnetic, and contraction when they are ferromagnetic. There is a critical ratio R_c = 1/2 between nnn- and nn-couplings, beyond which the SAF phase no longer exists.

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A. saguia, B. Boechat, O. F. de Alcantara Bonfim, J. Florencio. 2013-05-10. Phase transitions in the two-dimensional super-antiferromagnetic Ising model with next-nearest-neighbor interactions. https://doi.org/10.1103/physreve.87.052140

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