1. A spin-valve-like magnetoresistance of an antiferromagnet- based tunnel junction Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks Special thanks to : Josep Fontcuberta, Helena Reichlova, Pete Wadley, Joerg Wunderlich, Tomas Jungwirth Xavier Marti J. Zemen, V. Novak, B.G. Park, H. Reichlová, K. Olejnik, M. Cukr, O. Stelmakhovych, V. Holy, P. Nemec, P. Horodyska, E. Rozkotova, N. Tesarova, A. Shick, J. Masek, F. Maca, Y. Kurosaki, M. Yamada, H. Yamamoto, A. Nishide, J. Hayakawa, H. Takahashi, R. Campion, T. Foxon, B. Gallagher, P. Wadley, K. Edmonds, A. Rushforth, D. Petti, E. Albisetti, R. Bertacco, I.Fina, F. Sanchez, J. Fontcuberta, J. Wunderlich, T. Jungwirth 28.03.2012MPI Halle14:30

2. Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks Outline 1.Tunnel Anisotropic-Magnetoresistance. Strategy: large change in DOS(E F ) 2.Sample characterization: substrate/Py/IrMn/MgO/Pt layers 3.Spin-valve-like magnetoresistance IrMn/MgO/Pt 4.New strategy: large change of chemical potential at E F 5.I-II-V antiferromagnetic semiconductor: tetragonal LiMnAs/InAs 6.I-II-V antiferromagnetic semimetals: tetragonal CuMnAs/GaAs

3. FM insulator [AFM]

4. No-Mag FM insulator

5. Co Courtesy of Jan Zemen

6. Co Courtesy of Jan Zemen

7. No-Mag FM insulator

8. Park et al., PRL 100, 087204 (2008) Co: 0.1 %

9. Park et al., PRL 100, 087204 (2008) Co: 0.1 %

10. Park et al., PRL 100, 087204 (2008) CoPt: 10 % Co: 0.1 %

11. CoPtCo Courtesy of Jan Zemen

12. CoPtCo Courtesy of Jan Zemen

13. CoPtCo Courtesy of Jan Zemen

16. CoPtCo PtCo Park et al., PRL 100, 087204 (2008) CoPt: 10 % TAMR: Uniaxial anisotropy

17. CoPtCo PtCo Park et al., PRL 100, 087204 (2008) CoPt: 10 % TAMR: Uniaxial anisotropy M S-O M Schick et al., PRB 81, 212409 (2010)

18. 18 spontaneous moment spin-orbit coupling Ta/Ru/Ta MnIr MgO Pt NiFe Antiferromagnetic Bimetallic alloy IrMn is already present in TMR structure Intention is to remove NiFe from the stack and place IrMn at the barrier Schick et al., PRB 81, 212409 (2010)

19. CoPt: 10 % Co: 0.1 % IrMn: ? %

20. Q: How to rotate AFM-coupled staggered moments?

21. W.H. Meiklejohn, J. Appl. Phys. 33 (1962) 1328

22. Q: How to rotate AFM-coupled staggered moments? D. Mauri, J. Appl. Phys. 62 (1987) 3047

23. W.H. Meiklejohn, J. Appl. Phys. 33 (1962) 1328 K. Takano, Phys. Rev. Lett. 79 (1997) 1130 D. Mauri, J. Appl. Phys. 62 (1987) 3047 M. Kiwi, EPL 48 (1999) 573 A.P. Malozemoff, Phys. Rev. B 35 (1987) 3679 P. Miltenyi, Phys. Rev. Lett. 84 (2000) 4224 N.C. Koon, Phys. Rev. Lett. 78 (1997) 4865 M. Kiwi, EPL 48 (1999) 573 F. Radu, J. Phys.: Condens. Matter 18, L29 (2006) Inspired by F. Radu PhD Thesis and Josep Nogues Talk (Prague 2012) (Not an exhaustive list)

24. Ta/Ru/Ta MnIr MgO Pt NiFe From conventional FM-FM to AFM-based tunnel junction Park et al., Nature Mater. 10, 347 (2011) US patent 7939870

25. Ta/Ru/Ta MnIr MgO Pt NiFe From conventional FM-FM to AFM-based tunnel junction Park et al., Nature Mater. 10, 347 (2011) US patent 7939870

26. Ta/Ru/Ta NiFe MnIr MgO Pt From conventional FM-FM to AFM-based tunnel junction Park et al., Nature Mater. 10, 347 (2011) US patent 7939870

27. Ta/Ru/Ta NiFe MnIr MgO Pt From conventional FM-FM to AFM-based tunnel junction DOS(2) AFM FM DOS(1) Park et al., Nature Mater. 10, 347 (2011) US patent 7939870

28.  Structural and magnetic characterization of the samples (

29. From X-ray diffraction studies we learn that: 1.IrMn is cubic (c/a = 1) [1] 2.IrMn is in “disordered” gamma-phase [2] 3.IrMn is in-plane not ordered [3] 4.IrMn is out-of-plane textured, (111) [1-3] 5.Ir content is close to 30% 6.Grains are ~10 nm 7.Magnetic structure is likely Q3 1 2 3 IrMn(111) QxQx QyQy Marti et al., PRL 2012

31. From X-ray diffraction studies we learn that: 1.IrMn is cubic (c/a = 1) [1] 2.IrMn is in “disordered” gamma-phase [2] 3.IrMn is in-plane not ordered [3] 4.IrMn is out-of-plane textured, (111) [1-3] 5.Ir content is close to 30% 6.Grains are ~10 nm 7.Magnetic structure is likely Q3 1 2 3 IrMn(111) QxQx QyQy Marti et al., PRL 2012

32. GS = 1/0.01 = 100 A ~ 10 nm Marti et al., PRL 2012

33. 33 IrMn grain size ~ 10 nm Ru Ta Oxide Ta NiFe MgO IrMn

34. 1 2 3 IrMn(111) QxQx QyQy From X-ray diffraction studies we learn that: 1.IrMn is cubic (c/a = 1) [1] 2.IrMn is in “disordered” gamma-phase [2] 3.IrMn is in-plane not ordered [3] 4.IrMn is out-of-plane textured, (111) [1-3] 5.Ir content is close to 30% 6.Grains are ~10 nm 7.Magnetic structure is likely Q3 Marti et al., PRL 2012

35. PHYSICAL REVIEW B 67, 024420 (2003) The magnetic structure is likely to be θ ≈ 50.. 60 deg, so-called Q3 structure A C All spins contained in the (111) plane B Py Mn L 2,3 XMCD Net magnetic moment found in unpinned Mn DLS I06

36. PHYSICAL REVIEW B 67, 024420 (2003) The magnetic structure is likely to be θ ≈ 50.. 60 deg, so-called Q3 structure A C All spins contained in the (111) plane B Py Net magnetic moment found in unpinned Mn Only at the FM/AFM interface DLS I06

37. SQUID magnetometer F. Radu, S-G model M-B model Marti et al., PRL 2012

38. Ta/Ru/Ta NiFe MnIr MgO Pt From conventional FM-FM to AFM-based tunnel junction DOS(2) AFM FM DOS(1) Park et al., Nature Mater. 10, 347 (2011) US patent 7939870 ) TAMR SQUID Marti et al., PRL 2012

39. 3 mT 50 mT B B Park et al., Nature Mater. 10, 347 (2011) US patent 7939870

40. Marti et al., PRL 2012 AFM TAMR : electrical reading of AFM moments 10K

41. Marti et al., PRL 2012 AFM TAMR : electrical reading of AFM moments 10K

42. 42 AFM TAMR : irreversibility Park et al., Nature Mater. 10, 347 (2011) US patent 7939870 CoPt: 10 % Co: 0.1 % IrMn: 100 %

43. AFM TAMR: control sample without the AFM Park et al., Nature Mater. 10, 347 (2011) US patent 7939870

44. AFM TAMR : either uniaxial (EB-induced) or unidirectional anisotropy? At very low temperatures signal is strongly unidirectional… H eb >>1

45. 45 AFM TAMR : electrical reading of AFM moments R + ≠ R - R + = R - Marti et al., PRL 2012 Less TAMR = Less difference between initial and final states

46. 46 Marti et al, AFM TAMR : electrical reading of AFM moments R + ≠ R - R + = R - Marti et al., PRL 2012 Less TAMR = Less difference between initial and final states

47. SQUID magnetometer Marti et al., PRL 2012 K AF (T  300K)  0 J EB (T  300K)  0 If K AF is low it is easier to rotate, but if J eb is also low, coupling is also low, and the AFM-rotation smaller

48. SQUID magnetometer Marti et al., PRL 2012 K AF (T  300K)  0 J EB (T  300K)  0 If K AF is low it is easier to rotate, but if J eb is also low, coupling is also low, and the AFM-rotation smaller B(T) 300 K: The two “metastable” states are separated less than K B T

49. Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks Outline 1.Tunnel Anisotropic-Magnetoresistance. Strategy: large change in DOS(E F ) 2.Sample characterization: substrate/Py/IrMn/MgO/Pt layers 3.Spin-valve-like magnetoresistance IrMn/MgO/Pt 4.New strategy: large change of chemical potential at E F 5.I-II-V antiferromagnetic semiconductor: tetragonal LiMnAs/InAs 6.I-II-V antiferromagnetic semimetals: tetragonal CuMnAs/GaAs

50. Energy Density of states EFEF Tunnel transport  large change in DOS(EF) Charge control  large change in chemical potential

51. insulator Silicon transistor Energy EFEF Density of states

52. insulator Silicon transistor Energy EFEF Density of states

53. B ptp B 90 B0B0 I

54. Spin-dependent chemical potential shift in capacitively coupled gate instead of channel Ciccarelli, Zarbo, Irvine, Campion, Gallagher, Wunderlich, Jungwirth, Ferguson preprint ‘12

55. Common approach to spin-transistorInverted approach to spin-transistor

56. Doping Temperature Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks GaAs (Ga,Mn)AsMnAs Ferromagnetic Semiconductor

57. III-VFM T C (K)AFM T N (K) FeN100 FeP115 FeAs77 FeSb100-220 GdN72 GdP15 GdAs19 GdSb27 II-VIFM T C (K)AFM T N (K) MnO122 MnS152 MnSe173 MnTe323 EuO67 EuS16 EuSe5 EuTe10 Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks Intrinsic III-V and II-VI semiconductors Maca et al., JMMM 324, 1606 (2012)

58. Energy EFEF DOS

59. Crystal and magnetic structure: Bronger et al, Z. anorg. allg. Chem. 539, 175 (1986) THEORY Semiconductor with huge spin-orbit coupling Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks

60. InAs 4.27A 4.28A THIN FILM EPILAYERS V. Novak, et al., J. Cryst. Growth 323, 348 (2011)

61. log(intensity) InAs 4.27A 4.28A THIN FILM EPILAYERS

62. LiMnAs has a bandgap InAs LiMnAs 4.27A 4.28A I. Wijnheijmer et al, Appl. Phys. Lett. In press dI/dV map

63. Is LiMnAs the only choice available? Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks I

64. Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks V. M. Ryzhkovsky, et al., Inorg. Mater. 32 117 (1995) A.E. Austin, et al., J. Appl. Phys. 33 1356 (1962) TNTN RT CuMnAs, Mn 2 As prototype Courtesy of J. Zelezný

65. GaAs(004) GaAs(002) CuMnAs(001) CuMnAs(002) CuMnAs(003) CuMnAs(004) 6.30 Å (a) (b) (c) (d)

66. XRD Neutron d-spacing (Å)

67. 67 Summary TAMR in FM metalsTAMR in AF bimetallic alloys Park et al., PRL 100, 087204 (2008)Schick et al., PRB 81, 212409 (2010) Spin-valve-like magnetoresistance of an antiferromagnetic-based tunnel junction Park et al., Nature Mater. 10, 347 (2011) US patent 7939870 Electrical measurement of the AFM moments Marti et al, submitted 2011

68. Thanks for your attention !!! Xavier Marti, xavi.mr@gmail.comxavi.mr@gmail.com http://usuaris.tinet.cat/xmarti/talks Special thanks to : Josep Fontcuberta, Helena Reichlova, Pete Wadley, Joerg Wunderlich, Tomas Jungwirth Xavier Marti V. Novak, B.G. Park, H. Reichlová, K. Olejnik, M. Cukr, O. Stelmakhovych, V. Holy, P. Nemec, P. Horodyska, E. Rozkotova, N. Tesarova, A. Shick, J. Masek, F. Maca, Y. Kurosaki, M. Yamada, H. Yamamoto, A. Nishide, J. Hayakawa, H. Takahashi, R. Campion, T. Foxon, B. Gallagher, P. Wadley, K. Edmonds, A. Rushforth, D. Petti, E. Albisetti, R. Bertacco, I.Fina, F. Sanchez, J. Fontcuberta, J. Wunderlich, T. Jungwirth 28.03.2012MPI Halle14:30