Abstract
We study the free-induction decay and the spin-echo attenuation at long times for spins diffusing in a random magnetic field. We show that the decay of transverse magnetization in a Gaussian random longitudinal field is asymptotically M(t)∼, where γ is the exponent of a self-avoiding walk. The usual result given by a cumulant expansion fails due to correlations arising from multiple self-intersections in d≤4. Experimental relevance of our analysis is discussed along with the question of universality and the existence of large fluctuations in finite-size systems.
- Received 12 July 1991
DOI:https://doi.org/10.1103/PhysRevB.44.12035
©1991 American Physical Society