期刊
PHYSICAL REVIEW E
卷 84, 期 3, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevE.84.031132
关键词
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资金
- CAPES [0940-10-0]
- CNPq [302924/2009-4]
- FAPERJ [E-26/101.572/2010]
Transfer-matrix methods, with the help of finite-size scaling and conformal invariance concepts, are used to investigate the critical behavior of two-dimensional square-lattice Ising spin-1/2 systems with first-and second-neighbor interactions, both antiferromagnetic, in a uniform external field. On the critical curve separating collinearly ordered and paramagnetic phases, our estimates of the conformal anomaly c are very close to unity, indicating the presence of continuously varying exponents. This is confirmed by direct calculations, which also lend support to a weak-universality picture; however, small but consistent deviations from the Ising-like values eta = 1/4, gamma/nu = 7/4, beta/nu = 1/8 are found. For higher fields, on the line separating row-shifted (2 x 2) and disordered phases, we find values of the exponent eta very close to zero.
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