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Switching and Equilibration in All-Perpendicular Spin Valves Subject to Short Current Pulses

Switching and Equilibration in All-Perpendicular Spin Valves Subject to Short Current Pulses. H. Liu 1* , D. Bedau 1 , J. A. Katine 2 , E. E. Fullerton 3 , S. Mangin 4 , Z. Z. Sun 5 and A . D. Kent 1

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Switching and Equilibration in All-Perpendicular Spin Valves Subject to Short Current Pulses

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  1. Switching and Equilibration in All-Perpendicular Spin Valves Subject to Short Current Pulses H. Liu1*, D. Bedau1, J. A. Katine2, E. E. Fullerton3, S. Mangin4, Z. Z. Sun5 and A. D. Kent1 Department of Physics, New York University, 4 Washington Place, New York, New York 10003, USA San Jose Research Center, Hitachi-GST, San Jose, California 95135, USA CMRR, University of California, San Diego, La Jolla, California 92093-0401, USA IJL, Nancy-Université, UMR CNRS 7198, F-54042 VandoeuvreCedex, France IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598, USA

  2. Sample structure MR = 0.3% too small to record switching process in real time. [Co/Ni] x 4 • Co/Ni free layer, 1.6 nm thick • Co/Ni – Co/Pt hard layer • high coercive field (> 0.5 T) • Measured > 20 samples • Present results on: • 100 nm x 100 nm • 50 nm x 50 nm samples easy axis Cu [Co/Ni] x 2 / [Co/Pt] x 4

  3. Pulse measurement– fast pulse slow readout method • Information we cannot resolve: • Relaxation to the final state of the sample after the pulse if it has switched. • Or relaxation back to the initial state if it has not switched. Measure Rdc before pulse Pulse (~ ns) Measure Rdc after pulse ~ -100 ms 0 ~ 100 ms

  4. Double pulses a1 delay a2 a1 or a2 d1 d1 or d2 d2 • Study the dynamics after the first pulse by applying a second pulse with a delay (sub ns -> DC) Compare

  5. Relaxation to the final state Measurement Design Results • First pulse: switch from AP to P • Second pulse: cannot switch back from P to AP • We can resolve dynamics within ~ 100 ps • The relaxation time after the first pulse is ~ 0.5 ns AP –> P stay in P

  6. Relaxation to the initial state Measurement Design Results • First pulse: cannot switch from AP to P • Second pulse: can switch from AP to P • Switching probability (SP) decreases with longer delay • SP distributions collapse when delay is 0.5 ns or larger AP –> P stay in AP

  7. delay delay Analysis a a a a a d1 d1 d2 δt d2 + δt 1. Bedau et.al. arXiv: 1009.5240v1

  8. Modeling L: angular momentum in the sample L2 L0 L1 delay first pulse equal L0 single pulse L2

  9. Apply DC Current Another way to change the initial condition

  10. Duration scans for different Idcs

  11. Analysis

  12. Thank you!

  13. Switching in short time regime Universal behavior when duration is less than about 5 ns Switching Probability distribution only depends on the net charge

  14. P vsdelay for different DC currents

  15. Fitting parameters

  16. Free Layer Free Layer Free Layer Hard Layer Hard Layer Hard Layer

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