The European Physical Journal B (EPJ B)

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Eur. Phys. J. B 7, 105-109

Universality in three dimensional random-field ground states

A.K. Hartmann¹ - U. Nowak²

¹ Institut für theoretische Physik, Philosophenweg 19, 69120 Heidelberg, Germany
² Theoretische Tieftemperaturphysik, Gerhard-Mercator-Universität-Duisburg, 47048 Duisburg, Germany
hartmann@philosoph.tphys.uni-heidelberg.de, uli@thp.uni-duisburg.de

Received: 9 July 1998 / Received in final form: 15 July 1998 / Accepted: 20 July 1998

Abstract
We investigate the critical behavior of three-dimensional random-field Ising systems with both Gauss and bimodal distribution of random fields and additional the three-dimensional diluted Ising antiferromagnet in an external field. These models are expected to be in the same universality class. We use exact ground-state calculations with an integer optimization algorithm and by a finite-size scaling analysis we calculate the critical exponents $\nu$ , $\beta$ , and $\bar{\gamma}$ . While the random-field model with Gauss distribution of random fields and the diluted antiferromagnet appear to be in same universality class, the critical exponents of the random-field model with bimodal distribution of random fields seem to be significantly different.

PACS
05.70.Jk Critical point phenomena - 64.60.Fr Equilibrium properties near critical points, critical exponents - 75.10.Hk Classical spin models - 75.50.Lk Spin glasses and other random magnets

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