Depth sensitive exchange coupling in top and bottom pinned spin valve structures

Abstract

PACS 75.60. Ej, 75.70.Cn Top and bottom pinned spin valve structures have been fabricated using rf magnetron sputtering to study the depth sensitive exchange coupling. M-H curves of both the configurations in as-deposited and annealed forms have been measured by vibration sample magnetometry (VSM) and transverse Kerr effect spectrometry (TKE) using DC and AC magnetic fields, respectively. The TKE signal was also examined as a function of wavelength in the range from 300-800 nm, to obtain data from the full length of the bottom NiFe free layer covering either side of the interface. Annealing of the samples brings in higher values of exchange bias field compared to as-deposited samples perhaps due to improved uniformity in exchange conditions. The TKE data at 500 nm wavelength point towards energetically favourable spin structure at the pinned interface. Wavelength dependence of the TKE data shows an anamolous trend close to the NiFe-Cu (seed layer) inteface, which was attributed to a periodic Cu diffusion assisted non-specular reflection (diffraction) component.