Planar Hall effect and magnetoresistance in Co/Cu multilayer films

The magnetization reversal process and magnetotransport properties of [Co (10 nm)/Cu ( t Cu)/Co (10 nm)] 2 multilayer films have been investigated using a combination of planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) measurements. We have studied the effects of interlayer exchange coupling in the Co/Cu multilayer films by varying the thickness of the Cu spacer layer in the range 0≤ t Cu≤15 nm for fixed Co thickness. We observed marked changes in both the magnetic and magnetotransport properties for varied t Cu due to the effect of interlayer exchange coupling. For t Cu=5 nm, a complex magnetic spin state develops in the PHE output which may be attributed to anti-ferromagnetic coupling between the adjacent magnetic layers in contrast with ferromagnetic coupling observed for t Cu=2 nm. We have also made a direct comparison of AMR and PHE voltages as a function of the orientation of the constant applied field relative to the current direction. We observed that PHE output voltage is extremely sensitive to exact spin orientation when compared with AMR voltage measured simultaneously on the same device. When the applied field is less than the switching field of the device PHE voltage reveals a departure from the sin 2 θ behaviour predicted by theory due to domain wall propagation.