1 Department of Physics, New York University, New York, NY, USA. 2 Hitachi-GST, San Jose, CA, USA

1. Spin-transfer switching with short current pulses in all perpendicular magnetized spin valve nanopillars Bedau, Daniel1, Liu, Huanlong1, Bouzaglou, Jean-Jacques1, 4, Kent, Andrew D.1, Katine, Jordon A.2, Moyerman, Stephanie3, Fullerton, Eric E.3, Mangin, Stephane4 1Department of Physics, New York University, New York, NY, USA. 2Hitachi-GST, San Jose, CA, USA 3CMRR, University of California, La Jolla, CA, USA 4Institut Jean Lamour, Nancy Université, Vandoeuvre, France *db137@nyu.edu

2. Spin Transfer and Magnetic Anisotropy Ic~ UK large Hk Memory 1 Memory 2 Oscillator / Memory Kent et al., APL (2004) Ebelset al., Nat. Mat (2007) Lee et al., APL (2009) Papusoi et al., APL(2009) Beaujour et al., SPIE(2009) Mangin et al., Nat. Mater (2006) Mangin et al. APL (2009) Sun, PRB (2000)

3. Device Structure [Co/Ni]x2 easy axis [Co/Pt]x4 Co/Ni/Co • Co/Ni free layer • Co/Pt-Co/Ni hard layer • Size : 100 nm x 100 nm 50 nm x 50 nm

4. Transport Measurements 100 nm x 100 nm sample R=6 W B Current Source 0.3% MR

5. I-H Phase Diagrams 100 nm x 100 nm 50 nm x 50 nm • 95 mT coercive field. • 16 mT dipolar field. AP→P P→AP 100 nm x 100 nm • 100 nm x 100 nm thermally very stable.

6. Switching Probability Determination • Determining the switching probability for different fields/currents/durations. Pulse (1 mA, 1 ns) ? 1 2 3 4 B = 0.2 T B = 0 T Saturate Apply field Apply current Measure no Switched ? yes • The experiment is repeated 100-10000 times.

7. Switching Probability 100 nm x 100 nm 14 P=1 AP P • P to AP gives similar results P=0

8. Switching Probability • Minimal energy consumption at topt = 660 ps.

9. Dynamic Parameter A m0HK=0.25 T, a=0.011, P=0.015 θ0=1.36 rad • UK = 338 kT. • 19 mA/kT. (100 nm device) θ0=0.05 rad • Strong variation of A with field. • Large initial angle. • Process faster than predicted.

10. Conclusions & Outlook • Fast switching in all-perpendicular spin valves. • Optimal switching duration 660 ps. • UK/kT = 16…338 makes all-perpendicular devices a good candidate for STT-MRAM. • Macrospin model does not describe field dependence of dynamic behavior. Bedau et al., Appl. Phys. Lett. 96, 022514 (2010)

11. 50 nm x 50 nm switching • 1 mA switching current @ 5 ns.

12. 50 nm x 50 nm switching • m0Hc=0.188 T • Ic0=800 mA • U/kBT=68 • 2.6 mA switching current @ 500 ps.

13. LLG for Uniaxial Anisotropy • Field and current are aligned along the easy axis: Landau-Lifshitz-Gilbert (LLG) equation + Spin Torque: Thermal effects are described by the initial angular distribution – J. Z. Sun, P.R.B. 2000

14. Short Time Macrospin Model • is the final (initial) angle Leading-order solution for the switching current: “Dynamic Parameter” • Predicted switching time t: