Cross-sectional transmission electron microscopy study of the microstructure of electrodeposited Co-Ni-Cu/Cu GMR multilayers

In a previous work. we have established that for electrodeposited (ED) Co-N i-Cu/Cu multilayers the occurrence of giant magnetoresistance (GMR) and its magnitude sensitively depends on the deposition mode (potentiostatic or ga lvanostatic) and on the Cu substrate texture [(100) or (110)]. In order to have a better understanding of the influence of preparation conditions on t he magnetoresistance behaviour of these multilayers, we have now undertaken a detailed cross-sectional microstructural study on the same samples by co nventional and high-resolution transmission electron microscopy (TEM). It t urned out from this investigation that both, the microstructure and the pre ferred orientation of the mutilayers, are strongly influenced by the prepar ation conditions. For example, the multilayers with the highest GMR, which are grown potentiostatically on (100)-textured substrates, exhibit a column ar growth with (100) texture. The columns contain a high level of intermal strain, relaxed only to a small extent by lattice defects. Multilayers grow n galvanostatically on the same substrate, in contrast, have a(lll) texture with a large number of extended twins.