History dependent domain structures in giant-magnetoresistive multilayers

Resistance noise measurements of several types reveal the field history dependence of domain structure in sputtered Co/Cu multilayers. We find many smaller domains as the field is decreased from saturation towards zero, but as the field changes sign and is increased in the opposite direction we observe a smaller number of larger domains. Cycling the field without changing its sign preserves the smaller domains, strongly reducing the Barkhausen noise. Discrete fluctuations in resistance due to individual domains yield domain size estimates.© 1995 American Institute of Physics.