Dynamical effects and the critical behavior of Random-Field Systems (invited)

Conference · Sun Jan 01 04:00:00 EST 1984

OSTI ID:6297617

Shapir, Y

A variety of phemonena is observed experimentally in random-field (RF) systems realized by the application of an external field to diluted antiferromagnets. At low temperatures, infinitely long hysteric effects are manifested by the history dependence of the final states: long-range order is observed if the field is applied after final states, while domain-states are reached when field-cooled. While no indications for critical fluctuations are detected in 2d systems, scaling behavior, for both the correlation length and the specific-heat, is observed in 3d systems over an intermediate range of temperatures. The related critical properties seem to be well described by the corresponding ones in the 2d pure Ising model. The renormalization-group approach, which yields for the equilibrium critical exponents their values of the pure model in d-2 dimensions, is reviewed. A generalization of the dimensional-reduction approach, which accounts self-consistently for renormalized responses of the RF system, is presented. The dynamical effects are implicitly incorporated through the variation in the critical response between the local and the global regimes, associated with short and long time scales, respectively. In both regimes the lower critical dimension is found to be d = 2 in accordance with stability arguments. The short-time critical behavior indicates a dimensional-reduction by one for the 3d thermal exponents, in agreement with the experimental results. 36 references.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6297617
• Report Number(s): BNL-35371; CONF-841184-13; ON: DE85003209
• Country of Publication: United States
• Language: English

Related Subjects

656000* -- Condensed Matter Physics
657007 -- Electricity & Magnetism-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETIC MATERIALS
ANTIFERROMAGNETISM
CRYSTAL MODELS
ELECTROMAGNETIC FIELDS
ISING MODEL
MAGNETIC MATERIALS
MAGNETIC PROPERTIES
MAGNETISM
MATERIALS
MATHEMATICAL MODELS
PHYSICAL PROPERTIES
RENORMALIZATION