Mesoscopic Sized Spin-Glass Systems

We have been studying sub-micron sized wires and rings constructed from 400-600angstroms thick 1--- ppm CuMn material at temperatures down to 10 mK. These samples are in the regime where the voltage probes in a 4-point resistance measurement are spaced by a few spin-glass correlation lengths as implied from analysis of bulk nonlinear susceptibilities and thin film studies. The spin-dependent electron scattering then determines a resistance that senses the magnetic impurity configuration.