A tunneling magnetoresistance sensor overlaid with a longitudinal bias stack in a read region

Abstract

A tunneling magnetoresistance (TMR) sensor overlaid with a longitudinal bias (LB) stack in a read region is characterized in this study. The TMR sensor comprises Pt-Mn/Co-Fe/Ru/Co-Fe/Al-O/Co-Fe/Ni-Fe films, and the LB stack comprises Co-Fe/AFM (Ir-Mn or Pt-Mn) films. The Pt-Mn film of the TMR sensor is used to transversely pin its adjacent Co-Fe film and induce a transverse flux closure between the two Co-Fe films adjacent to the Ru film, thereby achieving proper sensor operation. The net moments of the two Co-Fe films (m2-m3) are optimized in order to induce an optimal demagnetizing field for optimal TMR responses. The AFM film of the LB stack is used to longitudinally pin its adjacent Co-Fe film and induce a longitudinal flux between the Co-Fe film and the Co-Fe/Ni-Fe sense layers, thereby achieving sensor stabilization. The moment ratio of the Co-Fe longitudinal-pinned layer to the Co-Fe/Ni-Fe sense layers (m4/m1) is optimized in order to achieve sensor stability while maintaining high signal sensitivity.