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Summary and prospects in the field of magnetically doped semiconductors

FunDMS. Summary and prospects in the field of magnetically doped semiconductors. Tomasz Dietl Laboratory for Cryogenic and Spintronic Research, Institute of Physics, Polish Academy of Sciences Institute of Theoretical Physics, University of Warsaw , Poland

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Summary and prospects in the field of magnetically doped semiconductors

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  1. FunDMS Summary and prospects in the field of magnetically doped semiconductors Tomasz Dietl Laboratory for Cryogenic and Spintronic Research, Institute of Physics, Polish Academy of Sciences Institute of Theoretical Physics, University of Warsaw, Poland WPI-AIMR Tohoku University, Sendai, Japan see, A. Bonanni and T. Dietl, Chem. Soc. Rev. 39, 528 (2010) T. Dietl and H. Ohno, Rev. Mod. Phys. 86, 187 (2014)

  2. FunDMS Summary and prospects in the field of magnetically doped semiconductors Tomasz Dietl Laboratory for Cryogenic and Spintronic Research, Institute of Physics, Polish Academy of Sciences Institute of Theoretical Physics, University of Warsaw, Poland WPI-AIMR Tohoku University, Sendai, Japan see, A. Bonanni and T. Dietl, Chem. Soc. Rev. 39, 528 (2010) T. Dietl and H. Ohno, Rev. Mod. Phys. 86, 187 (2014) • Unanticipated richness of materials science challenges • Test beds for spintronic functionalities

  3. Magnetically doped semiconductors • Accomplishments

  4. Magnetically doped semiconductors • Accomplishments • Prospects, challenges, emerging fields, …

  5. Magnetically doped semiconductors • Accomplishments • Prospects, challenges, emerging fields, … • Role of nuclear methods (other talks, discussion, ) characterization, fabrication, …

  6. Moessbauer isotopes

  7. Moessbauer isotopes and more …. channeling

  8. Outline Mamagnetically doped semiconductors summary, prospects, challenges, emerging fields, …

  9. Outline Mamagnetically doped semiconductors summary, prospects, challenges, emerging fields, … • dopants • semiconductors • magnetic interactions • magnetic ground states • functionalities

  10. Outline Mamagnetically doped semiconductors summary, prospects, challenges, emerging fields, … • dopants • semiconductors • magnetic interactions • magnetic ground states • functionalities The case study – magnetically-doped nitrides  Alberta Bonanni

  11. Dilute magnetic semiconductors (DMSs) III-V II-VI Al P Cr Zn S Cr Ga As Mn Cd Se Mn In Sb Fe Hg Te Fe Galazka ‘77

  12. Magnetic elements

  13. Magnetic dopants • Transition metals: open 3d shell but also 4d e.g. Ru • Rare earth: 4f but also actinides: 5f, e.g. U • Magnetically active defects and impurities • d0 ferromagnetism • p ferromagnetism • Contamination

  14. Magnetic dopants • Transition metals: open 3d shell but also 4d e.g. Ru • Rare earth: 4f but also actinides: 5f, e.g. U • Magnetically active defects and impurities • d0 ferromagnetism • p ferromagnetism • Contamination • doping methods: • also ion implantation, isotope transmutation, …

  15. Single impurity limit

  16. TM, RE doping – single impurity limit Questions answers depend on growth method/co-doping • incorporation into the lattice – not always cation substitution • energy levels • electrical activity • charge and spin state • Jahn-Teller distortion • hybridization with band states • defect generation • formation of complexes • with defects/impurities • …. T.D. (SST’2002)

  17. Interstitial position • e.g. part of Mn in MBE-(Ga,Mn)As) • Mn interstitials: • -- donors  compensate holes • -- form AF pairs with MnGa •  compensate spins K. M. Yu et al. (Berkeley, Notre-Dame, PRB’2012)

  18. Antisite position • e.g. part of Mn in • Mn-implanted(Ga,Mn)N - channeling L.M.C. Pereira et al. (Leuven, Lisboa) PRB'12

  19. Complexes • e.g. Mn-Mgkcomplexes in (Ga,Mn)N:Mg Mn T. Devillers et al. (Linz, Warsaw), Sci. Reports 2012

  20. Contamination • e.g. etched Si 300 K 300 K P. J. Grace et al. (TCD, Weizmann) Adv. Mat.’09

  21. Contamination • e.g. etched Si 300 K 300 K P. J. Grace et al. (TCD, Weizmann) Adv. Mat.’09

  22. Contamination • e.g. etched Si 300 K 300 K P. J. Grace et al. (TCD, Weizmann) Adv. Mat.’09  Fe from glass Fe-containing nanoparticles main source of ferro contamination

  23. Many impurities - DMS

  24. Distribution of magnetic dopants • Key insight • d orbitals contribute to bonding •  attractive force between TM cations (chemicalinteractions) •  non-random distribution of TM ions at thermal equilibrium • Exceptions (trueDMSs) • -- (II,Mn)VI • -- growth far from thermal equilibrium, e.g., LT-MBE of (Ga,Mn)As • Types of non-random distribution • -- crystallographic phase separation (precipitation) • -- chemical phase separation (spinodal decomposition) •  locally high density of TM  • condensedmagneticsemiconductors (CMS)

  25. e.g., annealed (Ga,Mn)As Hexagonal MnAs nanocrystals in GaAs Nanocrystals Cubic (Mn,Ga)As nanocrystals in GaAs M. Moreno et al. (Berlin) JAP’02

  26. 25nm wz-(Al,Cr)N zb-(Zn,Cr)Te Nanocolumns TEM/EDS N. Yotaro, et al. (Tsukuba, Warsaw) MRS Proc.’09 L. Gu et al. (Arizona) JMMM’06 (Ge,Mn) TEM/EELS M. Jamet et al. (Grenoble) Nature Mat. ’06 cf. D. Bougear et al.. (WSI Garching)

  27. Controlling TM distribution • TM distribution depends more on growth/processing • than on TM/host combination • Aggregation can be enhanced by • -- high growth temperature • -- slow growth rate • Can be affected by changing valence of TM ions • -- co-doping • -- electrical/optical carrier injection during growth

  28. ZnTe:N Cr+3 ZnTe EF Cr+2 EF Effect of doping on spinodal decomposition TM charge state is controlled by co-doping with shallow impurities. Because of Coulomb repulsion spinodal decomposition is blocked if TM is charged T.D., Nature Mat.’06 L.-H. Ye et al. (NWU) PRB’06

  29. Effect of co-doping on magnetism [I] ~ 2 x 1018 cm-3 Cr2+ Te-rich growth Cr2+/Cr3+ [N] ~ 3 x1020 cm-3 Cr3+ S. Kuroda … T.D. (Tsukuba, Warsaw) Nature Mat., ’07

  30. Optimized 50nm Effect of co-doping on Cr distribution I-doped TEM/EDS Inhomogeneous S. Kuroda ... T.D. (Tsukuba, Warsaw) Nature Mat., ’07

  31. Optimized 50nm N-doped Effect of co-doping on Cr distribution I-doped N-doped TEM/EDS Inhomogeneous Homogeneous S. Kuroda … T.D. (Tsukuba, Warsaw) Nature Mat., ’07

  32. Magnetic interactions between localized spins Dominant interaction in non-metals -- superexchange TM cation TM cation anion Always present: • usually antiferromagnetic, e.g. Mn2+ [reduces M(T,H)] DMS – random antiferromagnets spin-glass freezing at low T

  33. Zn1-xCoxO – inverse magnetic susceptibility grown by ALD at 160oC x = 42% M. Sawicki et al. [Warsaw] PRB’2013 antiferromagnetic superexchange

  34. Zn1-xCoxO – spin-glass freezing M. Sawicki et al. [Warsaw] PRB’2013

  35. Effects of TM spins on band states sp-d exchange interaction in DMSs H = - Isp-dsS -- spin disorder scattering -- formation of magnetic polarons -- giant spin splitting of bands proportional to magnetization of localized spins

  36. Giant splitting of exciton states ~ M(T,H) E ~ M ~ BS(H) c.b. v.b. geff > 102 J. Gaj et al., R. Planel,.. A. Twardowski et al. G. Bastard, … -- p-d: Ipd No- 1.0 eV large p-d hybridization and large intra-site Hubbard U => kinetic p-d exchange -- s-d: Isd No0.2 eV no s-d hybridization => potential s-d exchange

  37. Ferromagnetic superexchange TM cation TM cation anion • usually antiferromagnetic, e.g. Mn2+ [reduces M(T,H)] • sometimes ferromagnetic [enhances M(T,H)] eg. (Ga,Mn)N with Mn3+, TC up to 12 K  ferromagnetic Mott-Hubbard insulator cf. Alberta Bonanni

  38. RKKY and Bloembergen-Rowland mechanism spin polarisation of carriers spin polarisation of valence electrons  Dominates in topological insulators 4th order process in hybridisation <k|H |d>

  39. Zener/RKKY model of ferromagnetism Competition between entropy, AF interactions, and lowering of carrier enrgy owing to spin-splitting Curie temperatureTC = TCW = TF – TAFsuperexchange TF = S(S+1)xeffNo(s)(EF)I2/12 (s)(EF)~ m*kFd-2 (if no spin-orbit coupling, parabolic band) => TC ~ 50 times greater for the holes large m* large Ip-d T.D. et al. PRB’97,’01,‘02, Science ’00

  40. Making DMS ferromagnetic – p-type doping holes mediate ferro coupling in DMS source of holes in Mn-based DMSs, x < 10%: • Mn itself III-V (In,Mn)As; (Ga,Mn)AsH. Ohno et al. [IBM, Tohoku] PRL’92, APL’96 (Sb,Mn)2Te3;(Bi,Mn)2Te3Choi et al. [Ulsan] pps(b)’04 TC up to 190 K TC up to 20 K

  41. Making DMS ferromagnetic – p-type doping valence band holes mediate ferro coupling in p-type DMS source of holes in Mn-based DMSs, x < 10%: • Mn itself III-V (In,Mn)As; (Ga,Mn)AsH. Ohno et al. [IBM, Tohoku] PRL’92, APL’96 (Sb,Mn)2Te3;(Bi,Mn)2Te3Choi et al. [Ulsan] pps(b)’04 • acceptor impurities (Cd,Mn)Te:N, (Zn,Mn)Te:P TD, Cibert et al. [Grenoble, Warsaw] PRB’97, PRL’97, PRL’03 (K,Ba)(Zn,Mn)2As2et al. [Beijing, Columbia U.] Nat. Commun.’13 TC up to 190 K TC up to 20 K TC up to 5 K TC up to 180 K

  42. Making DMS ferromagnetic – p-type doping valence band holes mediate ferro coupling in p-type DMS source of holes in Mn-based DMSs, x < 10%: • Mn itself III-V (In,Mn)As; (Ga,Mn)AsH. Ohno et al. [IBM, Tohoku] PRL’92, APL’96 (Sb,Mn)2Te3;(Bi,Mn)2Te3Choi et al. [Ulsan] pps(b)’04 • acceptor impurities (Cd,Mn)Te:N, (Zn,Mn)Te:P TD, Cibert et al. [Grenoble, Warsaw] PRB’97, PRL’97, PRL’03 (K,Ba)(Zn,Mn)2As2et al. [Beijing, Columbia U.] Nat. Commun.’13 • cation vacancies IV-VI, [I-II]-V (Pb,Sn,Mn)TeT. Story et al. [Warsaw] PRL’86 (Ge,Mn)Te Y. Fukuma et al. [Yamaguchi] APL’08 [Li(Zn,Mn)]As Z. Deng et al. [Beijing, Columbia,Tokyo, Vancouver] Nature Comm.’11 TC up to 190 K TC up to 20 K TC up to 5 K TC up to 180 K TC up to 10 K TC up to 190 K TC up to 50 K

  43. TC in p-type (III,Mn)V p-d Zener model/expl. T.D. et al., Science’00 InSb:T. Jungwirth et al., PRB’02 Berkeley Prague/Nottingham/Beijing Kanagawa Tohoku Notre Dame

  44. High TC ferromagnetic semiconductors

  45. DMS, DMO, and non-magnetic materials showingspontaneous magnetization at 300 K wz-c-(Ga,Mn)N, (Ga,Fe)N, (In,Mn)N, (Al,Mn)N, (Ga,Cr)N, (Al,Cr)N (Ga,Mn)As, (In,Mn)As, (Ga,Mn)Sb, (Ga,Mn)P:C (Zn,Mn)O, (Zn,Ni)O, (Zn,Co)O, (Zn,V)O, (Zn,Fe,Cu)O, (Zn,Cu)O (Zn,Cr)Te (Ti,Co)O2, (Ti,V)O2, (Ti,Cr)O2, (Sn,Co)O2, (Sn,Fe)O2, (Hf,Co)O2 (Cd,Ge,Mn)P2, (Zn,Ge,Mn)P2, (Cd,Ge,Mn)As2, (Zn,Sn,Mn)As2 (Ge,Mn), (Ge,Cr), (Ge,Mn,Fe), (Si,Fe), (Si,Mn), (SiC,Fe) (La,Ca)B6, CaB2C2, C, C60, HfO2, ZnO, GaN:Gd, GaN:Eu... • holes unnecessary • TM ions unnecessary • confirmed by ab initio works in many cases • properties strongly dependent on the growth conditions

  46. Functionalities

  47. Magnetically-doped semiconductors - functionalities cf. Hannes Raebiger – ab initio Localized gap states -- carrier trapping (TM gap levels, Zhang-Rice polarons)  semi-insulating substrates GaAs:Cr, InP:Fe, GaN:Fe, …

  48. Magnetically-doped semiconductors - functionalities Localized gap states -- carrier trapping (TM gap levels, Zhang-Rice polarons)  semi-insulating substrates GaAs:Cr, InP:Fe, GaN:Fe, … -- intra-center optical transitions LEDs ZnSe:Mn  broad band optically pumped lasers oxides: TM, ZnSe:Cr, ... S. Mirov et al.. Laser & Photon. Rev. 4, No. 1, 21–41 (2010) Challenge: electrically pumped broadband lasers

  49. laser fiber (Cd,Mn)Te magnet Optical insulators of DMS • absorption (+) > (-)  magnetic circular dichroism  large Faraday rotation • optical isolators: J. Gaj, M. Nawrocki, R. Gałązka SSC’78 F = /4 spintronic device Challenge: optical isolators of ferromagnetic semiconductors

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