K. Dahmen et Jp. Sethna, HYSTERESIS, AVALANCHES, AND DISORDER-INDUCED CRITICAL SCALING - A RENORMALIZATION-GROUP APPROACH, Physical review. B, Condensed matter, 53(22), 1996, pp. 14872-14905
Hysteresis loops are often seen in experiments at first-order phase tr
ansformations, when the system goes out of equilibrium. They may have
a macroscopic jump (roughly as in the supercooling of liquids) or they
may be smoothly varying (as seen in most magnets). We have studied th
e nonequilibrium zero-temperature random-field Ising-model as a model
for hysteretic behavior at first-order phase transformations. As disor
der is added, one finds a transition where the jump in the magnetizati
on (corresponding to an infinite avalanche) decreases to zero. At this
transition we find a diverging length scale, power-law distributions
of noise (avalanches), and universal behavior. We expand the critical
exponents about mean-field theory in 6-epsilon dimensions. Using a map
ping to the pure Ising model, we Borel sum the 6-epsilon expansion to
O(epsilon(5)) for the correlation length exponent. We have developed a
method for directly calculating avalanche distribution exponents, whi
ch we perform to O(epsilon). Our analytical predictions agree with num
erical exponents in two, three, four, and five dimensions [Perkovic et
al., Phys. Rev. Lett. 75, 4528 (1995)].