A brief history with Ivan. Happy Birthday Ivan. You are now closer to 70!

Transcription

1 A brief history with Ivan Happy Birthday Ivan You are now closer to 70!

2 My brief history with Ivan 1986: I was a graduate student at UCSD, without a thesis advisor and not sure what I was going to do. Decided to talk to a new professor: Ivan Schuller I m too damn busy, talk to me next week We met next week and he explained a possible project: Ag/Co superlattices: Interest for perpendicular transport My lab is in Argonne so you will have to move there and then bring the lab back to UCSD. However, there was a test. I need to know today!

3 My brief history with Ivan Visit the Bruynserade Lab aka Prince Hiradi Also got to work in Prof. Bruynseraede s Lab (aka Prince Hiradi) Also got to work with a great number of people: M. Grimsditch, W. M. Robertson, H. Vanderstraeten, J.P. Locquet, D. Neerinck, K. Temst, O. Nakamura, J. Guimpel, J. Santamaria, D. Kelly, T. Moran, A. Fernandez, W. Hale, S. Bader, S. Sinha,..

4 Spin transfer torques in high anisotropy magnetic nanostructures S. Mangin 1, Y. Henry 2, D. Ravelosona 3, J.A. Katine 4, A. Kent 5, I. Tudosa 6, J. Kan 6, E. E. Fullerton NSF Award # DMR ANR-2010-BLAN-1005-FRIENDS

5 Spin transfer torques in high anisotropy magnetic nanostructures S. Mangin 1, Y. Henry 2, D. Ravelosona 3, J.A. Katine 4, A. Kent 5, I. Tudosa 6, J. Kan 6, E. E. Fullerton 6 Introduction Experimental results reversal current, time, and energy Conclusions NSF Award # DMR ANR-2010-BLAN-1005-FRIENDS

6 Spin transfer torques in heterostructures G p m Angular momentum conservation spin transfer torques Γ m d e L dt J. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996) L. Berger, Phys. Rev. B 54, 9353 (1996) see J. Magn. Magn. Mater. 320 (2008) articles on spin torque edited by Stiles and Ralph

7 Spin torque dynamics (LLG) dm dt 0 Hm Field torque (precession) m dm dt Damping torque (dissipation) H eff m

8 Spin torque dynamics (LLG) dm dt 0 Hm Field torque (precession) m dm dt Damping torque (dissipation) H eff m - IP g m i em t s B ( ( )) m x m x p Spin torque (negative friction ) I H C J. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996) 0 eff L. Berger, Phys. Rev. B 54, 9353 (1996)

9 Energy landscape In-plane devices perpendicular devices K // z 2-2M S K 2-2M S y x z z K eff y x x y Coercivity H C =2K // /M s H C =2K eff /M s Thermal energy E B = K // V E B = K eff V Effective field H K// + 2M s H K,eff =2K eff /M s

10 Stability analysis of the LLG equations H F1 F2 e- out-of-plane magnetization (H K > 4M S ) 2e M g ( ) V p ( H H ) I S C0 K, eff For H=0 I C 2e 0 g 2 E ( ) B p E B = 50k B T (0.2 aj)

11 nm 45 nm Nanopillars fabrication - Use of negative HSQ resist as a high fidelity mask devices/5 inch wafer: circles and hexagons from 45nm to 1500nm Au 100 nm Au I<0 Ta Cu Pt [Co/Ni]x4 Cu [Co/Ni]x2 [Co/Pt]x4 Pt H>0 Ta (5 nm) Cu (15nm) Pt (3nm) [Co/Ni] (3 nm) Cu (4nm) [Co/Pt]/[Co/Ni] (4nm Pt (3nm) Cu Ta Cu (35nm) Ta (5 nm) nm

12 Field switching in 50x100nm 2 nanopillars dv/di (Ohms) dv/di (Ohms) AP a) P Hc free = 2.65 koe Hc ref = 10 koe H d = 650 Oe H (koe) b) (111) - Co(1Å)/Ni(6Å) Pt [Co/Ni]x I B (ma) Cu [Co/Ni]x2 [Co/Pd] or [Co/Pt] Pt Mangin et al., Nature Mater. 5, 210 (2006)

13 Current induced switching in 50x100nm 2 nanopillars dv/di (Ohms) dv/di (Ohms) AP a) P Hc free = 2.65 koe Hc ref = 10 koe H d = 650 Oe H (koe) b) AP P I C AP-P = -2.6x10 7 A/cm 2 I C P-AP = 7x10 7 A/cm 2 I c (Co/Pt)4xI c (Co/Ni) I B (ma) Mangin et al., Nature Mater. 5, 210 (2006)

14 I C0 vs. Energy barrier

15 R AC () dv/di () dv/di () dv/di () R AC () dv/di () I c vs. Energy barrier Pt [Co/Ni]x4 Cu [Co/Ni]x2 [Co/Pt]x4 Pt RAC () nm nm H (Oe) I C 1.45 ma I C H c =2.65kOe 2e 0 g B ( ) p x 12 E H c =0.42 koe 31.0 Hdip= 0.8 koe app (koe) 0 H (koe) H app (koe) (c) (b) (c) [Co/Ni]x5 Cu [Co/Ni]x2 [Co/Pt]x4 Pt 45 nm I C 120 ma I DC (ma) I DC (ma) I DC (ma) S. Mangin et al Appl. Phys. Lett (2009)

16 Minimum Energy 1/t = A(I I C0 ) t = reversal time I = current I C0 = critical current to counter damping A = dynamics parameter

17 1/t = A(I I C0 ) Minimum Energy D. B. Bedau and A Kent, NYU Appl. Phys. Lett. 96, (2010).

18 Minimum Energy 1/t = A(I I C0 ) -Short times -Long times 50 nm x 50 nm Minimum Energy switching I = 2I C0 Most efficient when r=r Half power goes R and half goes to dissipation 18

19 Minimum Energy 1/t = A(I I C0 ) -Short times -Long times 50 nm x 50 nm Minimum Energy switching I = 2I C0 spins in the free layer ~10 electrons/spin There is a minimum energy pulse, ~0.8 ns with an energy of ~100 fj 19 Bedau et al. APL 96, (2010)

20 Conclusions Magneto-crystalline anisotropies can be used to tailor the energy landscape effective field spin torque reversal Perpendicular system I C0 scales with E B Minimum switching energy I=2I C0 Corresponds to 100 fj for 0.8 ns switching

21 Acknowledgements I.Tudosa J. Kan A. Kent Selected publications Mangin et al., Nature Materials 5, 210 (2006) Ravelosona et al., Phys. Rev. Lett. 96, (2006) Mangin et al., Appl. Phys. Lett. 94, (2009) Cucchiara et al., Appl. Phys. Lett. 94, (2009) Y. Henry et al., Phys. Rev. B, 79, (2009). S. Girod, et al., Appl. Phys. Lett. 94, (2009). D. Bedau, et al,appl. Phys. Lett. 96, (2010); D. Bedau, et al,appl. Phys. Lett. 97, (2011). NSF Award # DMR ANR-2010-BLAN-1005-FRIENDS

22 Final thanks I ve modeled much of my career on Ivan Student, post-doc and staff at ANL Work on exchange bias Modest hair loss Professor at UCSD Awards My good fortune started even as graduate student where I had the opportunity to work with a new professor at San Diego, Ivan Schuller. This was a fortuitous choice. He has mentored my career ever since and introduced me to the ideas of building materials by atomic layers that is the basis of much of the research that I do today.