Extraction of the Spin Glass Correlation
Length†
Dr. Y. G. Joh
UC, Riverside
Dept. of Physics
900 University Avenue
Riverside, CA 92521
(909)787-2482
yjoh@citrus.ucr.edu
The study of the irreversible behavior of the spin glass
magnetization under a change of magnetic field allows exploration of the available states
of a random frustrated system. There are various representations for the long time
evolution and the dynamics of spin glasses, even though a coherent, overall accepted real
space description remains lacking. The purpose of this presentation is to extract a time
and temperature dependent spin glass correlation length from a specially structured set of
experiments, and to compare our results with available theoretical predictions.
The peak of the spin glass relaxation rate, 
is directly related to the typical value
of the free energy barrier which can be explored over experimental time scales. We
identify the Zeeman energy Ez = Nsc fcH2, where c fc
is the field cooled susceptibility per spin, and Ns is the number
of correlated spins. The shift of the peak of S(t) gives Ez,
generating the spin glass correlation length, x (t,T) = Ns1/3.
Experiments on Cu : Mn 6at.% and CdCr1.7In0.3S4
can be fitted to both power law dynamics, x (t,T) µ ta (T) and
activated dynamics x (t,T) µ (lnt)1/y . These fits compare well
at simulation times scales with simulation fits to power law dynamics, but possess to
small a prefactor for simulation fits to activated dynamics.
† in conjunction with:
R. Orbach and G. G. Wood, University of California,
Riverside;
J. Hammann and E. Vicent, CEA Saclay, France