Critical spin dynamics in the two-dimensional percolating Ising antiferromagnet, Rb2CocMg1-cF4

Citation
S. Itoh et al., Critical spin dynamics in the two-dimensional percolating Ising antiferromagnet, Rb2CocMg1-cF4, J PHYS JPN, 70(10), 2001, pp. 3107-3111
Citations number
23
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
ISSN journal
0031-9015 → ACNP
Volume
70
Issue
10
Year of publication
2001
Pages
3107 - 3111
Database
ISI
SICI code
0031-9015(200110)70:10<3107:CSDITT>2.0.ZU;2-V
Abstract
We performed inelastic neutron-scattering experiments with high energy reso lution, in order to investigate the critical spin dynamics in the two-dimen sional (2D) Ising antiferromagnet, Rb2CoeMg1-cF4, with c = 0.6, 0.65, 0.7 a nd 1, above the percolation threshold c(p) (c(p) = 0.593 for a square latti ce). First, we have confirmed the dynamical scaling for the homogeneous sys tem (c = 1), and the observed dynamical critical exponent (z = 2.01 +/- 0.0 5) was very close to that obtained from recent numerical studies. Next, the observed spin dynamics in the dilute systems could be described by the tem perature dependence expected by the standard scaling theory, the power of t he, reduced temperature, however, the values of the exponents deviate from those predicted by the 2D Ising model and increase as c approaches to c, fr om the homogeneous limit. Also, the observed spin dynamics for c close cp w as in a quantitatively good agreement with that predicted by the model for critical spin dynamics in a percolating Ising system, in which the nature o f the spin dynamics is determined by the requirement to overcome, via therm al excitation, energy barriers to the overturning of the spins in domains r esulting from the inhomogeneous geometry of the percolating network. Althou gh we could not directly detect the difference in the functional form betwe en that expected by the standard scaling theory and that predicted by the p ercolation model in the present experimental condition, we conclude, from t he quantitative agreement, that the critical spin dynamics in Rb2CoeMg1-eF4 with e close to and just above c(p) is well described by the percolation m odel.