Effect of annealing on magnetotransport and structural properties of Co∕Cu multilayers with Ta buffer layer

Abstract

The main aim of this study is to investigate the effect of annealing on magnetotransport and on structural properties of Co∕Cu multilayer with Ta buffer layer, prepared by dc magnetron sputtering. The heat treatment of the sample at 250°C up to 20h induced a prominent change in giant magnetoresistance, which correlates with the corresponding changes in remanent magnetization. In order to investigate the origin of the changes in the magnetotransport properties, the microstructure of the samples has been studied by x-ray diffraction. The structural modifications were elucidated by comparing x-ray spectra calculated using a nonideal step model with measured spectra and they are related to the changes in magnetotransport properties. A correlation between the changes in remanence and interlayer exchange coupling has been established using a modified Stoner-Wohlfarth [Philos. Trans. R. Soc. London, Ser. A 240, 599 (1948)] model.

Effect of annealing on magnetotransport and structural properties of Ni70Co30/Cu multilayers

“…Although Ni 70 Co 30 /Cu multilayers show quite a high value of the GMR effect and low saturation [3,4], an irreversible degradation of the GMR occurs at elevated temperatures. However, the mechanisms leading to this degradation have not yet been explored in detail [5][6][7][8][9][10][11]. In particular, it is unclear how the spin-dependent scattering mechanisms are affected.…”

“…So a deeper insight into the correlation between the magnetotransport and the structural properties of Ni 70 Co 30 /Cu multilayers is necessary to improve the thermal stability of GMR devices. It is generally accepted that the GMR effect is connected with the spin-dependent scatter of interfaces [12] and the magnetic and transport properties of multilayers are closely related to their interfacial structure [13][14][15]. With increasing annealing temperatures, the structure of Ni 70 Co 30 /Cu multilayers gets modified due to interdiffusion 0022-3727/08/035001+07$30.00 at the interface or due to the changes in the interfacial roughness.…”