Rezonansowe jądrowego rozpraszanie promieniowania synchrotronowego czyli: Druga młodość efektu Mössbauera

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1 Rezonansowe jądrowego rozpraszanie promieniowania synchrotronowego czyli: Druga młodość efektu Mössbauera 1

2 AGH T. Ślęzak W. Karaś K. Matlak M. Ślęzak M. Zając IKiFP Kraków N. Spiridis K. Freindl D. Wilgocka-Ślęzak ESRF Grenoble R. Rüffer A.I. Chumakov S. Stankov Uni. Wien B. Sepiol G.Vogl M. Rennhofer M. Sladecek IKS Leuven B. Laenens INP Kraków K. Parliński J. Łażewski NMP4-CT DYNASYNC Dynamics in Nano-scale Materials Studied with Synchrotron Radiation 2

3 Efekt Mössbauera w synchrotronie Koherentne elastyczne rozpraszanie jądrowe: 20 lat później: Pola nadsubtelne na powierzchni Fe NIS Anty-Efekt Mössbauera..i jeszcze coś 3

4 Mössbauer spectroscopy: Recoilless, resonance adsorption of γ-radiation structural, chemical and electronic information on a local scale (mainly 57 Fe) 4

5 Conventional (energy-domain) MS I=1/2 E=E 0 (1 ±v/c) I=3/2 57 Fe Only one transition is excited at the same time, therefore the resultant spectrum is the incoherent sum of the indivitual transitions (the intensities are added). 5

6 Tunable source of EM radiation in Mössbauer transition range v E = ± E ± c µev 6

7 Hyperfine splitting of nuclear levels Γ 5 nev e - E hf 100 nev E = kev E hf 100 nev 57 Fe is hf spectroscopy with SR possible? hf spectroscopy in energy domain requires a tuneable source of X-rays with energy monochromatization ~5 nev (feasible is 0.5 mev) 7

8 Hyperfine spectroscopy with SR? -YES however not in energy - but in time-domain - Nuclear Resonance Scattering of SR - NRS Reproduced from: R. Röhlsberger, Nuclear Condensed Matter Physics with Synchrotron Radiation, Springer

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10 Ψ f Ψ i D-NRS GI-NRS Al CEMS SRPAC NIS NFS 10

11 Methodology Prompt scattering: electronic Delayed scattering: nuclear 11

12 Nuclear Resonance Scattering of SR - NRS Nuclear Inelastic Scattering of SR - NIS (precisely Inelastic Nuclear Resonant Adsorption) E i E 0 E i =E 0 ± E Intensity E phonon 0 e - phonon annihilation E 14.4 kev Phonon creation #2 Detectors # E(meV) log(counts) Time / ns 12

13 Instrumentation ID 18, ESRF Grenoble High Resolution Monochromator e - Storage ring High-heat-load monochromator Resonant sample undulator focussing collimation 13

14 High-heat heat-load premonochromator and high-resolution nested monochromator Si (4 2 2) high heat load monochromator Si (1 1 1) Si (12 2 2) Si (12 2 2) Si (1 1 1) E= kev high resolution monochromator Si (4 2 2) E: 300 ev 3 ev 2.5 mev 0.5 mev 14

15 Mössbauer isotopes with used in synchrotron-based experiments R. Röhlsberger et al. Phys. Rev. B 67, (2003) 15

16 Instrumentation ID 18, ESRF Grenoble High Resolution Monochromator e - Storage ring High-heat-load monochromator Resonant sample undulator focussing collimation 16

17 Instrumentation ID 18, ESRF Grenoble SR-beam Fast detector #2 NRS chamber on 2-circle goniometer Fast detector #1 17

18 1.2 mm 0.8 mm Dodatkowe ogniskowanie 90 µm 60 µm fotonów/s K-B multilayers 15 µm 15 µm 18

19 Nuclear Resonance Scattering of SR - NRS Nuclear Inelastic Scattering of SR - NIS (precisely Inelastic Nuclear Resonant Adsorption) E i E 0 E i =E 0 ± E Intensity E phonon 0 e - phonon annihilation E 14.4 kev Phonon creation #2 Detectors # E(meV) log(counts) Time / ns 19

20 Nuclear Resonance Scattering of SR - NRS 57 Fe Mössbauer isotope τ 0 = 141 ns e - E 14.4 kev I e =3/2 I g =1/2 20 delayed intensity ~ e -t/ τ 0 Quantum beats Decoherency by diffusion (accelerated decay) Log (Intensity) time [ns]

21 Geometry of GI-NRS 21

22 Orientation of the hyperfine field (the Smirnov figures ) z z B E y x B E z B y x E y x k k k Intensity (arb. units, log. scale) Time after excitation (ns)

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24 Depth selectivity time [ns] 24

25 t [ns] t [ns] 25

26 Model systemfe(110)/w(110) [110] - Large lattice mismatch ~10% -layer-by-layer growth - Pseudomorphic 1 st (?) and 2 nd (??) Fe atomic layer - Complex strained Fe structure beyond 2 nd AL - Complex magnetic structure with several transitions [001] Film thickness in AL Å 200x200nm 2 200x200nm 2 200x200nm 2 26

27 Surface magnetism 57 Fe(110) probe layer Epitaxial 56 Fe(110) film 20 Atomic Layers (AL) 10 3 B hf =32.5 T QS=0.10 mm/s 10 2 B hf =32.0 T QS=0.18 mm/s W(110) single crystal 10 4 B hf =34.2 T QS= Time / ns Time / ns 27 J.Korecki, U.Gradmann, Phys. Rev. Lett. 55(1985)2491.

28 NRS movie growth of Fe on W(110) 57 Fe 1-28 ML 57 Fe UHV Beam Fast detector 28

29 Fe/W(110) interface Sample: log(intensity) 33T 20T time [ns] AFM order at the Fe/W(110) interface 29

30 Nuclear Resonance Scattering of SR - NRS Nuclear Inelastic Scattering of SR - NIS (precisely Inelastic Nuclear Resonant Adsorption) E i E 0 E i =E 0 ± E Intensity E phonon 0 phonon annihilation Phonon creation E(meV) e - E 14.4 kev #2 Detectors #1 log(counts) Time / ns 30

31 Analiza danych doświadczalnych Widmo NIS Cząstkowe DOS-y dla Fe g(e,s) r d q r r g( E, ˆ) s = V ω q 2 0 δ [ E h ( )] ˆ ) 3 j q s ˆ ej ( j (2π ) S(E) 10 5 Pik elastyczny Anihilacja fononu Kreacja fononu k r photon êx Geometria poślizgu ˆ s ˆ ez 0 ê z êy ˆ s = Metoda nieczuła na wibracje normalne r k k photon photon E(meV) Fononowe DOS-y g(e) bezparametrowo S S ( E ) 1 ( E ) = f ( ) + ( ) + ( LM δ E S E S E n n =2 = E E g ( E ) ( βe 1 e ) R 1 ) 31

32 Intensity Od widm NIS do gęstości stanów - magnetyt T=296K T=140K T=120K T=100K T=25K E (mev) B. Handke et al. Phys. Rev. B T=296K T=140K T=120K T=100K 0.04 T=25K energy (mev) DOS (1/meV) 32

33 Monowarstwowa sonda 57 Fe w epitaksjalnej warstwie Fe(110) na W(110) 57 Fe(110) probe layer Epitaxial 56 Fe(110) film 20 Atomic Layers (AL) W(110) single crystal _ [110] [001] 100x100nm 2 75 ev 33

34 Widma czasowe Surface Fononowe DOS-y (cząstkowe: warstwowe i kierunkowe) Surface Counts B HF = T QS = 0.83 mm/s (QS=4*ε) B HF = T QS = 0.02 mm/s Sub-Surface Very deep Phonon density of states / mev [001] [1-10] Sub-Surface Very deep 10 3 B HF = T QS = 0.00 mm/s Time / ns Interface Dynasync, submitted E(meV) 34

35 Modelowanie Phonon DOS / mev along [001] along [1-10] E(meV) J. Łażewski, J. Korecki, K.Parliński, Phys. Rev. B,

36 Czy przybliżenie Debye pracuje na powierzchni? DOS (mev -1 ) Surface Sub-surface "Very" deep Bulk Phonon DOS / mev S S-1 D Bulk E(meV) E 2 (mev 2 ) Dynasync, submitted 36

37 Właściwości termo-elastyczne [1-10] [001] Kierunek wiązki X <x 2 > [Å] <γ> [N/m] Entropia [k B /atom] S S-1 D Bulk [1-10] [001] E T E T E T Stała siłowa r 2 M r 2 2 ln(f γ(s) =< ω > M = g(e,s)e de x = 2 h 2 k LM ) Dynasync, submitted Wnioski: brak widocznego tłumienia fononów powierzchnia jest harmoniczna. powierzchniowe drgania normalne są miękkie 37

38 Synchrotronowe zaburzone korelacje kątowe SRPAC detector Al 38

39 SRPAC dynamika w fazie ciekłej (f LM 0) Organic glass (DBP) (Tg = 178 K) doped with 5% (mol) of ferrocene Relaxation damps beats: SRPAC damping rate ~rotational dynamics NIS damping rate ~ rotational + translational dynamics 39

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41 10 18 Sensitivity (No. of atoms) foil monolayer single atoms 10 nm Year 41

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