Noise in NiFeCo/Cu spin valve sensors

Noise properties of FeMn/NiFeCo/Cu/NiFeCo spin valve sensors have been investigated for various sensor widths. The spin valve thin films were patterned into stripes of varying widths from 2 mu m to 20 mu m. The width-to-length ratio was kept constant giving a fixed resistance of about 840 Omega. The spin valve sensors have been configured to allow signal and noise measurements to be performed using a bridge system. Noise measurement in spin valves with parallel anisotropy axes and cross anisotropy axes show field dependent noise near the high sensitivity region around zero bias field. In spin valves with parallel anisotropy axes, the noise increases with decreasing sensor width but for the cross anisotropy configuration, the noise decreases with decreasing sensor width. As the applied alternating field is increased, the noise peaks splits into two centred at zero bias. This can be explained in terms of a degenerate energy state. (C) 2000 Elsevier Science S.A. All rights reserved.