Effect of stray-field coupling on active spin-valve elements analyzed by Lorentz transmission electron microscopy

In situ experiments using Lorentz transmission electron microscopy have bee n performed on 10 mu mX30 mu m active spin-valve elements through which a c urrent is applied during observation of the magnetization reversal of the s ense layer. It is shown that the reversal mechanism and the change in resis tance are very different depending on the relative orientations of the easy axis versus the applied field. The results show clearly that the contribut ions of the magnetostatic fields, due to either ferromagnetic coupling or s tray-field coupling, are higher than that of the field induced by the sensi ng current. A model is proposed to predict the offset of the giant magnetor esistance curves with respect to zero field. This model has been found to b e in good agreement with the experimental results. (C) 1999 American Instit ute of Physics. [S0021-8979(99)03408-8].