Switching and equilibration in all perpendicular spin valves subject to short current pulses
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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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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. 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


Sample structure
Sample structure Subject to Short Current

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


Pulse measurement fast pulse slow readout method
Pulse measurement Subject to Short Current – 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


Double pulses
Double Subject to Short Current 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


Relaxation to the final state
Relaxation to the final state Subject to Short Current

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


Relaxation to the initial state
Relaxation to the initial state Subject to Short Current

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


Analysis

delay Subject to Short Current

delay

Analysis

a

a

a

a

a

d1

d1

d2

δt

d2 + δt

1. Bedau et.al. arXiv: 1009.5240v1


Modeling
Modeling Subject to Short Current

L: angular momentum in the sample

L2

L0

L1

delay

first pulse

equal

L0

single pulse

L2


Apply dc current
Apply DC Current Subject to Short Current

Another way to change the initial condition


Duration scans for different i dc s
Duration scans for different Subject to Short Current Idcs


Analysis1
Analysis Subject to Short Current


Thank you
Thank you! Subject to Short Current


Switching in short time regime
Switching in short time regime Subject to Short Current

Universal behavior when duration is less than about 5 ns

Switching Probability distribution only depends on the net charge


P vs delay for different dc currents
P Subject to Short Current vsdelay for different DC currents


Fitting parameters
Fitting parameters Subject to Short Current


Switching and equilibration in all perpendicular spin valves subject to short current pulses

Free Layer Subject to Short Current

Free Layer

Free Layer

Hard Layer

Hard Layer

Hard Layer


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