RANDOM-FIELD-INDUCED SPIN-GLASS-LIKE BEHAVIOR IN THE DILUTED ISING ANTIFERROMAGNET FE0.31ZN0.69F2

The evolution of the d = 3 random-field Ising model (RFIM) in the strong-dilution limit has been studied using Faraday-rotation techniques on the Ising antiferromagnet Fe0.31Zn0.69F2. Particular attention has been given to the external field (H) dependence of the phase transition T(c)(H) and the equilibrium boundary T(eq)(H) in the range 0 less-than-or-equal-to H less-than-or-equal-to 7 T. For H < 1 T, both T(N)-T(c)(H) and T(N)-T(eq)(H) scale as H2/phi, with phi = 1.42, the universal d = 3 random-exchange-to-RFIM crossover exponent. However, as the field is increased above H = 1. 5 T, a striking reversal of the curvature of T(eq)(H) versus T is observed, now scaling with H as does the de Almeida-Thouless replica symmetry-breaking line in a conventional, exchange-frustrated spin glass, T(N)-T(eq)(H) almost-equal-to H2/phi, with phi = 3.4. Other spin-glass-like behavior is seen at higher fields such as the time dependence of the hysteretic properties of the remanent magnetization. These observations suggest it is the large random field that induces spin-glass-like behavior in this diluted antiferromagnet, without significant (if any) exchange frustration being present.