Interlayer interaction in giant magnetoresistive multilayers

The effect of interlayer interactions on the magnetization process in giant the magnetoresistive multilayers was investigated by studying sheet film samples of multistacked trilayers (MSTLs). First, a NiFe/Cu/Co trilayer was designed to have a magnetic moment ratio of 3:2 for NiFe:Co respectively. The thickness of the copper wall made to be greater than 2.5 nm in order to reduce the exchange coupling between the magnetic layers. The parallel and antiparallel states were easily obtained in the trilayer because the coercivities for NiFe and Co are sufficiently different and there were no apparent interactions between the layers. Upon stacking the trilayers to make a multilayer, the shape of the hysteresis loop became distorted. The implication of this distortion is that there is interaction between the magnetic layers that prevents a fully antiparallel alignment of the NiFe and Co magnetizations. This was determined by comparing the NiFe and Co magnetic moment ratios using vibrating sample magnetometry. The measured moment ratio increased at a rate of 2.3 per trilayer in the MSTL.