Microstructure and giant magnetoresistance behavior of amorphous CoNbZr based pseudo spin-valves with symmetric layer structures

The effects of amorphous CoNbZr layer on the microstructures and giant magnetoresistance (GMR) behavior of pseudo spin-valve (PSV) have been investigated by comparing two types of sandwiches, CoNbZr/Cu/Co (CNZ-PSV) and Co/Cu/CoNbZr (Co-PSV). X-ray reflectivity experiment and high-resolution transmission electron microscopy show that CNZ-PSV has smooth interfaces, while the Co-PSV has rough interfaces and a Co-Cu mixed layer forms between Co and Cu layers. Those defects are believed to induce strong magnetostatic coupling and cripple the GMR effect. Further researches show that the Cu on Co layer has a loose structure, while the Cu on CoNbZr is flat, dense and pinholes-free. Upon proper thermal annealing, the CoNbZr (2.6 nm)/Cu (2.2 nm)/Co (3 nm) has a large GMR enhancement to 9% and a superior thermal stability up to 350 deg. C. These results indicate that the amorphous CoNbZr soft layer can also act as a buffer layer and promotes excellent microstructure quality of the sandwich stack