Ground State Structure, Domain Walls, and External Field Response in Random Magnets.

摘要

The ground state structure and domain walls in Ising-like magnets with quenched randomness are studied at zero temperature. The methods employed are exact ground state calculations using graph-theoretical optimization and extreme statistics argument. The elastic manifolds, i.e., domain walls, with random-based disorder are investigated with two different types of periodicity. The first type of periodicity is when the randomness is periodically repeated. It is shown to lead after a cross-over to the periodic elastic media universality class, whenever the period lambda is finite. The second periodicity is due to an additional modulating potential. There are two types of intermittence seen before the asymptotic random-bond roughness behavior is reached. The first type is when the manifolds jump between the minima of the periodic potential and the second type is when the interfaces roughen over pinning energy barriers.