Spin transfer effect in spin-valve pillars for current-perpendicular-to-plane magnetoresistive heads (invited)

Abstract

Large spin-transfer effects were observed in spin-valve pillars developed for current-perpendicular-to-plane (CPP) magnetoresistive heads. The investigated samples are complex stacks including laminated free, synthetic/laminated pinned, and nano-oxide layers. The magnetoresistive (MR) transfer curves exhibit current-dependent loop shift and in some particular ranges of current and field, very large noise associated either to stochastic jump of the free layer magnetization or to excitations of steady precessional modes. A very unusual phenomenon of inverted coercivity was observed in the low current range. The spin-transfer effects show an asymmetry as a function of current direction. These experimental results indicate that the spin-transfer effects must be considered in the design of CPP MR heads.