Random-field critical behavior of a d = 3 Ising system: Neutron scattering studies of Fe/sub 0. 6/Zn/sub 0. 4/F/sub 2/

Journal Article · Mon Apr 01 04:00:00 EST 1985 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.31.4538· OSTI ID:6035247

Belanger, D P; King, A R; Jaccarino, V

The effects of random fields on the critical scattering of neutrons in a d = 3, diluted Ising antiferromagnet have been observed for the first time. The experiments were made on the same crystal of Fe/sub 0.6/Zn/sub 0.4/F/sub 2/ in which earlier birefringence (..delta..n) studies showed a sharp phase transition T/sub c/(H) to exist. Only the scattering in the region above T/sub c/(H) was studied, where hysteretic behavior is absent. In this equilibrium region, new random-field critical behavior is observed, indicative of an approach to a sharp, second-order phase transition at T/sub c/(H), unlike the d = 2 case where rounding of the phase transition occurs within the same region. Hence the lower critical dimensionality of the equilibrium random-field Ising model (RFIM) is bounded by 2< or =d/sub l/<3. The critical scattering is well described by S(q) = A/(kappa/sup 2/+q/sup 2/)+B/(kappa/sup 2/+q /sup 2/)/sup 2/, with A scaling as kappa/sup eta-bar/ and B as kappaeta-bar. A preliminary analysis yields nu-bar = 1.0 +- 0.15, gamma-bar = 1.75 +- 0.20, and eta-barapprox. =(1/4) for the random-field thermal correlation length (kappa/sup -1/), staggered susceptibility (chi/sub st/), and correlation function () critical exponents, respectively.

• Research Organization: Physics Department, Brookhaven National Laboratory, Upton, Long Island, New York 11973
• OSTI ID: 6035247
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 31:7; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ANTIFERROMAGNETIC MATERIALS
COHERENT SCATTERING
CRYSTAL FIELD
CRYSTAL MODELS
DIFFRACTION
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
IRON COMPOUNDS
IRON FLUORIDES
ISING MODEL
MAGNETIC MATERIALS
MATERIALS
MATHEMATICAL MODELS
NEUTRON DIFFRACTION
PHASE TRANSFORMATIONS
RANDOMNESS
SCATTERING
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
ZINC FLUORIDES
ZINC HALIDES