New memory effect in ferro/antiferromagnetic multilayers

Previous magnetization and ferromagnetic resonance measurements showed that when coupling was observed between ferromagnetic layers separated by an an tiferromagnetic NiO layer, it was always ferromagnetic. Here we report magn etization measurements that explain this result. We find that the coupling is only strongly ferromagnetic when the sample is cooled with the two ferro magnetic layer magnetizations parallel. Cooling with the magnetizations ant iparallel causes the coupling to become nearly zero. Thus, the coupling ret ains a memory of the relative orientation of the ferromagnetic layer magnet izations during cooling. (C) 2000 American Institute of Physics. [S0021-897 9(00)59708-4].