Conductance fluctuations of mesoscopic spin glasses

Abstract

Magnetoresistance measurements on 1000-ppm CuMn mesoscopic spin-glass samples reveal phase-coherent electron propagation on 0.4-\ensuremath{\mu}m length scales observed as conductance fluctuations and Aharonov-Bohm resistance oscillations. Exploiting the broken time-reversal symmetry of the spin-glass state, a unique magnetofingerprint of the specific frozen spin configuration is extracted from a pair of resistance measurements. These ``spin-glass fingerprints'' are manifestly different after several thermal histories, but are surprisingly robust upon field cycling to over 9 times the typical exchange field.