Multilevel Transitions of Closely Arranged Spin Valve Pillars Using Spin Transfer Switching

Two closely arranged spin valve pillars sharing a pair of top and bottom electrodes were fabricated and their spin transfer switching (STS) characteristics were investigated. Each pillar was a 300 times 100 nm rectangle, such that the distance d between two pillars was varied up to 1
mu
m . The STS curves of a single pillar and closely arranged pillars with the distance
d
of 1
mu
m showed single-step transitions, but the STS curves of closely arranged pillars with the distance
d
of 0.3
mu
m showed clear two-step transitions. We found that the plateau width of the intermediate resistive state of the two-step transitions can be controlled by the distance >
d
. The basis for this stable intermediate resistive state seemed to be magnetic interactions and the intrinsic switching mode of STS.