1 / 22

H. Liu [1]* , D. Bedau [1] , D. Backes [1] ,

Statistical and Time Resolved Studies of Switching in Magnetic Tunnel Junction based Orthogonal Spin Transfer Devices. H. Liu [1]* , D. Bedau [1] , D. Backes [1] , J. A. Katine [2] , J. Langer [3] , and A. D. Kent [1] [1] Department of Physics, New York University, New York, NY 10003 USA

edward-collier
Download Presentation

H. Liu [1]* , D. Bedau [1] , D. Backes [1] ,

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Statistical and Time Resolved Studies of Switching in Magnetic Tunnel Junction based Orthogonal Spin Transfer Devices H. Liu[1]*, D. Bedau[1], D. Backes[1], J. A. Katine[2], J. Langer[3], and A. D. Kent[1] [1] Department of Physics, New York University, New York, NY 10003 USA [2] San Jose Research Center, Hitachi-GST, San Jose, California 95135 USA [3] Singulus Technologies AG, 63796 Kahl am Main, Germany *: presenter Appl. Phys. Lett. 97, 242510 (2010) March Meeting 2012, Boston Massachusetts

  2. Outline • Sample • Design • Goal: fast, reliable switching • Why orthogonal geometry? • Fast • Switching • Sample characterization • Fast switching & low energy cost • Real-time • Measurement • Transition within 200 ps • Possible precessional switching March Meeting 2012, Boston Massachusetts

  3. Switching in collinear devices • No initial spin torque, if no thermal fluctuation • Waiting for large thermal fluctuation • Incubation delay (~ ns) • Unpredictable switching process m mp Polarizing layer electron Switchable layer March Meeting 2012, Boston Massachusetts

  4. Switching in orthogonal devices A.D. Kent et al., Appl. Phys. Lett. 84, 3897(2004) -Bdemag t=T/2 t=T • Merits: • Large initial torque. • Fast switching process. • Deterministic switching. • Low power consumption. t=0 Current • Differences from collinear: • Bipolar switching. • Precessional switching. March Meeting 2012, Boston Massachusetts

  5. Sample structure Appl. Phys. Lett. 97, 242510 (2010) SAF: PtMn CoFe Ru (AF coupled) CoFeB Barrier: MgO Free layer: CoFeB (3 nm) Spacer: Cu Polarizer: CoNi/CoPd March Meeting 2012, Boston Massachusetts

  6. Typical hysteresis TMR 100 %, RA~ 5 Ωμm2 Size: 40 nm x 80 nm ~ 80 nm x 240 nm. Shape: rectangles, ellipses and hexagons. Characterized: tens of thousands of samples. March Meeting 2012, Boston Massachusetts

  7. Magnetic field Fast switching measurements Switching only happens during the current pulse 1 2 Current Pulse Measure R Measure R’ 3 Compare R, R’ not switch 2 switched 3 Apply the same pulse 100 – 10,000 times 1 2 March Meeting 2012, Boston Massachusetts

  8. Previous Results 60 x 180 nm2, Hexagon MR = 107%, Rp = 400 Ω Hc = 14 mT • Fast switching • 100 % under 500 ps • No nano-seconds incubation delay • Low energy cost • -0.6 V, 500 ps • 400 Ω < R < 800 Ω • 225 fJ < E < 450 fJ Appl. Phys. Lett. 97, 242510 (2010) March Meeting 2012, Boston Massachusetts

  9. Bi-polar switching P->AP Switching e- e- 50 x 100 nm2, Rect. MR = 112%, Rp = 2.2 kΩ Hc = 8 mT Negative voltage favors P state according to the STT of the RL Positive voltage favors AP state according to the STT of the RL March Meeting 2012, Boston Massachusetts

  10. Real-time measurements e- Most switching duration < 200 ps. start switch March Meeting 2012, Boston Massachusetts

  11. Precessional switching Precess and switch to AP state Precess and remain in P state March Meeting 2012, Boston Massachusetts

  12. Conclusion • Fabricated OST-MRAM devices that incorporate magnetic tunnel junctions • Achieved high TMR (>100%) with low RA~ 5 W mm2 and perpendicular polarizer with excellent characteristics: high spin-polarization and large perpendicular magnetic anisotropy • Demonstrated 100% switching probability in thermally stable elements with 500 ps duration pulses (0.7 V), requiring just 450 fJ. • Can time-resolve individual switching events showing fast and precessional switching. Appl. Phys. Lett. 97, 242510 (2010) March Meeting 2012, Boston Massachusetts

  13. Thank you ! March Meeting 2012, Boston Massachusetts

  14. Switching statistics March Meeting 2012, Boston Massachusetts

  15. Switching statistics March Meeting 2012, Boston Massachusetts

  16. Bipolar and non–monotonic • Bipolar switching: • Appears for both P-> AP and AP-> P switching • The torque originates from the perpendicular polarizer • Heating is not an important mechanism since SP is different for different polarities • Non – monotonic switching: • Clearly appears in P -> AP switching with Vp > 0 and AP -> P switching with Vp< 0 • Qualitatively consistent with the deterministic switching Appl. Phys. Lett. 97, 242510 (2010) March Meeting 2012, Boston Massachusetts

  17. Switching in zero effective field 50 nm x 150 nm rectangular Hc = 8.5 mT A = -0.45 V March Meeting 2012, Boston Massachusetts

  18. Material hysteresis March Meeting 2012, Boston Massachusetts

  19. Magnetic field Fast switching measurements Switching only happen during the current pulse 1 2 Current Pulse Measure R Measure R’ 3 Compare R, R’ not switch 2 switched 3 2 1 Apply the same pulse 100 – 10,000 times March Meeting 2012, Boston Massachusetts

  20. Spin Torque • Spin torque – the amount of transverse angular momentum transferred in unit time. e mp electron m magnetization March Meeting 2012, Boston Massachusetts

  21. Spin Transfer Devices 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. Mat. (2006) Mangin et al., APL (2009) Sun, PRB (2000) Bedau et al., APL (2010) March Meeting 2012, Boston Massachusetts

  22. March Meeting 2012, Boston Massachusetts

More Related