Random fields and three-dimensional Ising models: Co/sub x/Zn/sub 1-x/F/sub 2/

Journal Article · Thu Sep 01 04:00:00 EDT 1983 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.28.2602· OSTI ID:5487131

Hagen, M; Cowley, R A; Satija, S K; Yoshizawa, H; Shirane, G; Birgeneau, R J; Guggenheim, H J

The phase transition and ordering of the d = 3 diluted Ising antiferromagnet Co/sub x/Zn/sub 1-x/F/sub 2/ has been studied using two-axis neutron diffraction for the cases (i) where x is close to the percolation threshold, in zero applied magnetic field, and (ii) as a function of applied magnetic field for samples with x = 0.26 and 0.35. The results of the percolation study show complicated behavior, probably due to concentration gradient problems. Nevertheless, there is strong evidence that the inverse correlation length decreases to zero at the onset of long-range order. The results of the magnetic field study are compared with the theoretical predictions for the d = 3 Ising model in a random field. It is found that when the samples are cooled in even the smallest (nonzero) fields the long-range magnetic order is destroyed and that the structure factor is well described by the Lorentzian plus Lorentzian squared form. The inverse correlation length is found to have a power-law dependence on the applied magnetic field at low temperature with exponents ..nu../sub H/ = 2.17 +- 0.3 for the x = 0.26 sample and ..nu../sub H/ = 3.63 +- 0.3 for the x = 0.35 sample. This result is not consistent with the current theoretical predictions for the field dependence of the inverse correlation length in the d = 3 Ising model in a random field. The measurements also show that the system is frozen at low temperatures and this freezing may be responsible for the discrepancy between theory and experiment.

• Research Organization: Department of Physics, University of Edinburgh, Mayfield Road, Edinburgh EH93JZ, Scotland, United Kingdom
• OSTI ID: 5487131
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 28:5; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ANISOTROPY
ANTIFERROMAGNETIC MATERIALS
COBALT COMPOUNDS
COBALT FLUORIDES
COHERENT SCATTERING
CORRELATIONS
CRYSTAL MODELS
CRYSTAL-PHASE TRANSFORMATIONS
DATA
DIFFRACTION
EXCHANGE INTERACTIONS
EXPERIMENTAL DATA
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
INFORMATION
INTERACTIONS
ISING MODEL
MAGNETIC FIELDS
MAGNETIC MATERIALS
MATERIALS
MATHEMATICAL MODELS
NEUTRON DIFFRACTION
NUMERICAL DATA
PHASE TRANSFORMATIONS
RANDOMNESS
SCATTERING
STRUCTURE FACTORS
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
ZINC FLUORIDES
ZINC HALIDES