Manipulation of the magnetization of Perpendicular magnetized Rare-earth-transition metal alloys using polarized light

Size: px

Start display at page:

Download "Manipulation of the magnetization of Perpendicular magnetized Rare-earth-transition metal alloys using polarized light"

Arabella Hood
5 years ago
Views:

1 Manipulation of the magnetization of Perpendicular magnetized Rare-earth-transition metal alloys using polarized light S. Mangin

2 7th Framework Program for Research IEF : Intra-European Fellowships IOF : International Outgoing Fellowships IIF : International Incoming Fellowships IOF IEF IIF Optical Probe and Manipulation of Magnetization at the nanometer scale

3 Nancy Nancy (France) Nancy

4 Institut Jean Lamour Born from 5 laboratories merging : 400 peoples Nano-science Surface science Nuclear Fusion Metallurgy Jan 2015 : New common building

5 Nanomagnetism /Spintronic 2 technicians, 2 CNRS researcher, 7 faculty members, 6 Ph.D & Post-Doc

6 Magnetization & Spin manipulation Magnetic Field Heat Polarized Current e - H Electric Field Light Strain E

7 Outlines Introduction All optical switching Our goals All optical switching for TbCo Influence of composition Influence of thickness Devices How to record magnetization switching in TbCo

8 All optical switching 40 fs pulses, 1 khz repetition 20 nm thick Gd22Fe74.6Co3.4 C.D. Stanciu et al, Phys. Rev. Lett. 99, (2007) Jan 31st 2013 IEEE Magnetic Society

9 Light induced magnetization reversal All-optical switching with circularly polarized light (40 fs single pulses) Stanciu et al., PRL 99, (2007) GdFeCo All-optical writing works without any applied external magnetic field All-optical writing event depends on combination magnetization and laser helicity All-optical switching only works above a certain fluence threshold

10 What is (are) the mechanism(s)? Magnetic field created by a laser beam Light Heat transfer by the laser Angular momentum transfer by the laser Still under discussion

Magnetic field Could reach several Tesla? 1.0 0.5 Sign depends on polarization m z 0.0-0.5 Short field pulse -1.0-1.0-0.5 0.0 m x 0.5 1.

11 Magnetic field Could reach several Tesla? Sign depends on polarization m z Short field pulse m x m y From LLG equation 100 ps field pulse is needed LLB? H IFE ~ 0.52kOe J.M. Li et al J. Appl.Phys. 111, 07D506 (2012)

12 Heat Ferrimagnetic material is needed Doesn t depends on polarization Will depend on pulse length Radu et al., Nature 472, 205 (2011)

13 Angular Momentum transfer Sign depends on polarization Light transfers little angular momentum

14 What are the Interactions / Time scales Field switching Spin Transfer Slow Fast

15 What are the important parameters? Polarization? 20 nm thick Gd 22 Fe 74.6 Co fs pulse 1 khz repetition Pulse length? Fluence? Repetiton? Laser Thickness? Rare earth Transition metal? Ferrimagnetic? Composition? Material

16 Why RE-TM alloys? ferrimagnetic RE-TM alloy rare earth transition metal alloy (Gd, Tb) (Fe, Co,Ni) (GdFeCo)

17 The materials : Ferrimagnetic alloys Tb X Co 1-X M M Tb M M Tb M Co M Co M M Tb M Co M RE = g RE (γ ) A RE M TM = g TM (γ ) A TM g RE = g TM Angular Momentum Compensation at T A Magnetization Compensation at T M

18 Can we use it? Magnetic data storage, Magnetic Memories, Magnetic Logic? Low energy 10 fj to switch 20 nm x 20 nm Fast Magnetizations reversal in 100 fs Phys Rev B 86, (R) (2012) High density? High Perpendicular Magnetic anisotropy Detectable? Can a current read Magnetization orientation

19 Our Goal Demonstrate AOS for other materials Better understanding Find material compatible with application requirement Tune parameters Magnetization Thickness Build devices

20 All-optical switching in TbCo AG Aeschlimann: circular polarized LASER beam, spot size: 20 µm 1 mm

AOS TbCo vs GdCo Tb 0.26 Co 0.74 Ferrimagnetic H C = 6 000 Oe H K = 6 T Close to compensation t= 20 nm 400 fs and 10ps = = = = = = = Gd 22 Fe 74.

21 AOS TbCo vs GdCo Tb 0.26 Co 0.74 Ferrimagnetic H C = Oe H K = 6 T Close to compensation t= 20 nm 400 fs and 10ps = = = = = = = Gd 22 Fe 74.6 Co 3.4 Ferrimagnetic H C = 400 Oe Low H K Close to compensation t= 20 nm 50 fs All-optical switching for a high anisotropy material ( ~ 4x10 6 ergs/cm 3 )

22 Amorphous structure of Co 1-x Tb x alloys Cu(2nm) /Pt(2nm) capping Co 1-x Tb x (t nm) substrate + Ta(5nm) buffer Co 74 Tb 26 Au 25 nm Transmission electron microscopy: I [a.u.] d Tb-Tb =3.52 Å d Co-Tb =3.01 Å d Co-Co =2.50 Å d C-C = 1.54 Å 25 nm /d [1/Å] è Co 1-x Tb x amorphous for 12% x 26%

23 Perpendicular anisotropy M [ka/m] 400 x=16% x=23% M [ka/m] x =16% x =23% µ 0 H [T] µ 0 H [T] H H è Co 1-x Tb x has PMA for 8% x 34%

24 Tunable magnetization M [ka/m] 600 M S T = 300 K Tb m m Co Co Tb Tb m Co Co m Tb x M [ka/m] è 0 M (x,t) 600 ka/m M. Gottwald, et al J. Appl. Phys (2012) m = m Tb -m Co Co m Tb m Co Tb 50 x = 20 % T [K] T comp = 280 K

25 Tunable Perpendicular Magnetic Anisotropy 2.0 K u K eff T = 300 K x = 12 x = 16 x = 20 x = 23 x = 26 K [MJ/m 3 ] x [at.%] T [K] è Origin of PMA unclear è 50 kj/m 3 K (x,t) 1600 kj/m 3

26 Composition influence on AOS T [K] Conclusion m 0 T comp T Curie only thermal effects Co Tb all-optical x Tb,vol [%] only thermal effects m Tb Co AOS observed close to compensation AOS observed above compensation

27 Understanding At T A any torque is very efficient Magnetic field created by a laser beam Not efficient Heat transfer by the laser Bring the sample to T A Angular momentum transfer by the laser Switching at T A Stanciu et al, Phys. Rev. B 73, (2006)

28 Influence of the composition

29 Influence of concentration and pulse duration S. Alebrand et al., Appl. Phys. Lett. 101, (2012)

30 Thickness dependence Competition between: Heat transfer Angular momentum transfer

31 Model Magnetic field created by a laser beam Heat transfer by the laser + Angular momentum transfer by the laser

32 Applications Data Storage Memories Logic Read Data

33 Transport measurements to Read Anisotropic Magnetoresistance (AMR) M I θ ΔR(M) = (R - R )cos 2 (θ) è M I Extraordinary Hall Effect (EHE) I M V+ V - ΔR ( ) ( I M ) M = R EHE è M plane ez M I Giant Magnetoresistance (GMR) M 1 M 2 I ΔR ( M ) = GMR M M 1 1 è θ(m 1,M 2 ) M M 2 2 2

Transport properties of CoTb alloys MgO/Co 88 Tb 12 /MgO 200 µm I U 800 µm U H U H I U ρ H /ρ [%] ΔR/R [10 3 ] 1.0 0.5 0.0-0.5-1.0 0.6 0.3 0.

34 Transport properties of CoTb alloys MgO/Co 88 Tb 12 /MgO 200 µm I U 800 µm U H U H I U ρ H /ρ [%] ΔR/R [10 3 ] H 1 m m H µ 0 H [T] m m m H H=0 H µ 0 H [T] è Complementary tools to observe magnetization reversal

Spin valves Co 74 Tb 26 m Tb Co 1 2 3 200 µm Co 88 Tb 12 m Tb Co 800 µm è Decoupled soft & hard layer è EHE Sign positive for Co sublattices è GMR sign : Co sublattices è Small GMR (low polarization,

35 Spin valves Co 74 Tb 26 m Tb Co µm Co 88 Tb 12 m Tb Co 800 µm è Decoupled soft & hard layer è EHE Sign positive for Co sublattices è GMR sign : Co sublattices è Small GMR (low polarization, short electron mean-free path?) C. Bellouard et al Phys. Rev. B 53, (1996) M. Jan Gottwald 31 st 2013 IEEE et al Magnetic Phys. Rev. Society B 85, (2012) ρ H /ρ [%] m [a.u.] GMR [%] µ0h [T]

36 Conclusion Demonstration of AOS for TbCo Composition and thickness dependence Model based on Heat + Angular momentum transfer TbCo reversal may be probed using transport measurements S. Alebrand et al., Appl. Phys. Lett. 101, (2012) M. Gottwald et al Phys. Rev. B 85, (2012) M. Gottwald, et al J. Appl. Phys (2012)

37 Acknowledgments Michel Hehn Martin Aeschlimann Daniel Lacour Sabine Alebrand Mirko Cinchetti Daniel Steil Eric E. Fullerton Matthias Gottwald

International French-USA Workshop Toward Low Power Spintronic Devices July 8th

edu/iwst/ Contact information: Iris Villanueva e-mail: ivilla@ucsd.edu A.

OHNO: Tohoku University (Japan) * B. DIENY: Spintec (France) * J. Z.

LEE: Qualcomm- San Diego (USA)* D. RALPH: Cornell University (USA) * A.

SUZUKI: Ozaka University (Japan) T.ONO, Kyoto University (Japan)* V.

OTANI: University of Tokyo and RIKEN (Japan) * L.

APALKOV: Samsung Electronics - Grandis (USA) * D.

38 International French-USA Workshop Toward Low Power Spintronic Devices July 8th - 12th, 2013 La Jolla, California Contact information: Iris Villanueva ivilla@ucsd.edu A. FERT (Nobel Prize 2007): CNRS/ Thales (France) * S.S.P. PARKIN : Stanford / IBM Almaden (USA)* H. OHNO: Tohoku University (Japan) * B. DIENY: Spintec (France) * J. Z. SUN: IBM-Yorktown Height (USA) * J. A. KATINE: HGST-WD- San Jose (USA)* I. SCHULLER : UC San Diego (USA) * A. THIAVILLE: University Paris Sud (France) * K. LEE: Qualcomm- San Diego (USA)* D. RALPH: Cornell University (USA) * A. HOFFMANN: Argonne National Laboratory (USA)* Y. SUZUKI: Ozaka University (Japan) T.ONO, Kyoto University (Japan)* V. LOMAKIN: UC San Diego (USA)* Y. OTANI: University of Tokyo and RIKEN (Japan) * L. PREJBEANU : Crocus (France) L.VILA: INAC-CEA (France) * D. APALKOV: Samsung Electronics - Grandis (USA) * D.L STEIN: New York University (USA)* J.ÅKERMAN: University of Gothenburg (Sweden)* *confirmed speakers Abstracts (see template online) must be submitted before March 1, Posters and oral presentations will be selected by the scientific committee and authors will be informed of the selection by April 1st. Registration will be accepted until June 1st

SUPPLEMENTARY INFORMATION

SUPPLEMENTARY INFORMATION Engineered materials for all-optical helicity-dependent magnetic switching S. Mangin 1,2, M. Gottwald 1, C-H. Lambert 1,2, D. Steil 3, V. Uhlíř 1, L. Pang 4, M. Hehn 2, S. Alebrand 3, M. Cinchetti 3, G.