The spin flop of synthetic antiferromagnetic pinned layers (SAF), under a m
agnetic field has been theoretically predicted and recently reported [J. G.
Zhu and Y. Zheng, IEEE Trans. Magn. 34, 1063 (1998); J. G. Zhu, IEEE Trans
. Magn. 35, 655 (1999)]. However, no experimental data have yet being repor
ted to confirm the theoretical prediction. This article will provide direct
experimental evidence to confirm the spin flop phenomenon in SAF layers. A
spin valve, [CoFe/NiFe]/Cu/[CoFe(II)/Ru/CoFe(I)]/IrMn, was used to verify
the spin flop in SAF layers. The exchange bias direction of CoFe(I)/IrMn wa
s introduced by a magnetic annealing process at 225 degrees C with a field
strength of H-an(10 kOe) and the exchange bias direction was found parallel
to the magnetic field. These samples serve as the reference for the remain
ing experiments. By magnetic annealing the reference samples at 225 degrees
C with lower magnetic fields, we found that the magnetic field threshold f
or SAF spin flop is about 1 kOe. When the field is further increased, the s
pins of CoFe(I) and CoFe(II) scissor toward the applied magnetic field axis
and the moment of the SAF reaches saturation when the applied field is equ
al to or greater than 10 kOe. Thus the above experiments demonstrate the fl
op behavior of the SAF. It also provides direct evidence that the exchange
bias direction between a ferro/antiferromagnetic interface is determined by
the magnetization of the ferromagnetic layer, not by the magnetic annealin
g field. (C) 2000 American Institute of Physics. [S0021-8979(00)59308-6].