Karl Johnston ISOLDECERN 40mes Journes des Actinides Sunday

Karl Johnston ISOLDE/CERN 40èmes Journées des Actinides Sunday 28 Match 2010 cern. ch/isolde-ssp

Outline of talk Ø Introduction to SSP @ ISOLDE Ø Experiments running Ø Infrastructure Ø Techniques used Ø Case studies using PAC and Mossbauer Spectroscopy Ø Future directions

Radioactive isotopes for solid state physics? Why & How? ? Nothing is more easy to detect with high sensitivity than nuclear radiation, i. e. very low concentrations of radioactive impurity atoms in a material can be detected. The radioactive isotopes (“probes”) act as “spies” transmitting information with atomic resolution via their decay. Crucial point: what information do you get? ? ? Adds extra dimension to “normal spectroscopies” e. g. optical / electrical characterisation of semiconductors Provides extremely local probe which is applied to variety of systems You need A facility providing a large variety of radioactive isotope (if possible, isotopically clean) You have to introduce the isotopes into the semiconductor 3 Øby ion implantation Øby diffusion Øduring crystal growth Øby nuclear reaction with one of the constituents of the solid

ISOLDE table of elements isotopes of this element used for solid state physics or life science

SSP @ ISOLDE: Diverse community Solid State physics: Semiconductors, Metals Materials scientists: High Tc Superconductors, Multiferroic materials Surface physics/Quantum Transport Biophysics: structural properties & role of heavy metals in proteins, DNA. SSP investment: money & people Participating Countries Participating Institutes Postdocs/professors/researchers Graduate Students (estimate) 21 41 50 50

Expt No. IS 501 Title of proposal Emission Mössbauer spectroscopy of advanced materials for Gunnlaugsson, H. (Aarhus), Sveinn Olafsson (Reykjavik) opto- and nano- electronics LOI 88 Beta. NMR as a novel technique for biological applications LOI 84 ASPIC 2 Radioactive probe studies of coordination mechanisms of heavy LOI 81 metal ions from natural waters to functionalized magnetic nanoparticles IS 492 Spokesperson/ Affiliation Defects in Zn. O, Cd. Te, and Si: Optical, structural, and electrical characterization Experiment Category Semiconductors (magnetism) Lars Hemmingsen/Monika Stachura (Copenhagen) Biophysics Kay Potzger Surface physics (magnetism/Quantum Transport) (FZ, Rossendorf, Germany) Vitor Amaral CICECO, Aveiro, Portugal (BIO)PHYSICS (cleaning water) Manfred Deicher TPUS, Saarbrücken, Germany SEMICONDUCTORS(defects characterization) Radiotracer diffusion in semiconductors and metallic compounds Manfred Deicher TPUS, Saarbrücken, Germany using short-lived isotopes Ag(I), Pb(II) and Hg(II) binding to biomolecules studied by Perturbed Lars Hemmingsen RVAUDNS, Frederiksberg, IS 488 Angular Correlation of γ-rays (PAC) spectroscopy: Function and Denmark toxicity of metal ions in biological systems IS 489 SEMICONDUCTORS(diffusion) BIOPHYSICS(detoxification) IS 487 Study of Local Correlations of Magnetic and Multiferroic Compounds Vitor Amaral CICECO, Aveiro, Portugal MULTIFERROICS(magnetism, dielectric… IS 486 Crystal field investigations of rare earth doped wide band gap semiconductors Ulrich Vetter PIUG, Göttingen, Germany SEMICONDUCTORS(wide band gap) IS 481 The role of In in III-nitride ternary semiconductors Katharina Lorenz ITN, Sacavém, Portugal SEMICONDUCTORS(ternary) Karl Johnston TPUS, Saarbrücken, Germany SEMICONDUCTORS(fundamental) IS 472 High Resolution optical spectroscopy in isotopically-pure Si IS 464 (n, p) emission channeling measurements on ion-implanted beryllium Uli Köster ILL, Grenoble, France Ulrich Wahl ITN, Sacavém, Portugal SEMICONDUCTORS & OXIDES (lattice location dopants) Räisänen, J. Helsinki SEMICONDUCTORS (diffusion) Hemmingsen, L. Frederiksberg Biophysics IS 443 Mössbauer studies of dilute magnetic semiconductors Marco Fanciulli INFN, Milano, Italy SEMICONDUCTORS(magnetism) IS 432 Diffusion of 52 Mn in Ga. As Räisänen, J. Helsinki SEMICONDUCTORS(diffusion) IS 425 Radioactive probes on ferromagnetic surfaces Wolf-Dietrich Zeitz (INTER)SURFACES(fundamental) IS 453 Emission channelling lattice location experiments with short-lived isotopes METALS / R&D IS 450 Diffusion of 56 Co in Ga. As, Zn. O and Si 1 -x. Gex systems IS 448 Pb(II) and Hg(II) binding to de novo designed proteins studied by 204 m. Pb- and 199 m. Hg-Perturbed Angular Correlation of g-rays (PAC) spectroscopy: clues to heavy metal toxicity HMI, Berlin, Germany

RIB solid state physics as applied nuclear physics Nuclear probes Radioactive Nuclei g, a, b Interactions Hyperfine Interaction Radioactive decay Muons ß+ Nuclear Physics Ions Neutrons Positrons Coulomb Interaction Scattering, Diffraction Nuclear Reaction ß+-e. Interaction Methods Mößbauer effect gg angular correlation Nuclear Magnetic resonance Nuclear orientation DLTS Photoluminescence Tracer Diffusion Emission Channeling Ion Channeling Backscattering Elastic Recoil Resonant Scattering Neutron Scattering Nuclear Reaction Analysis Positron Annihilation Positron Angular Distribution Positron Energy Distribution Solid state physics applications

Two-Photon PERTURBED ANGULAR CORRELATION Hyperfine splitting Electric field gradient / Magnetic hyperfine field Probe nucleus: Vzz - EFG principal component Q – quadrupolar moment - Asymmetry parameter - magnetic moment Bhf - Magnetic hyperfine field Ei E Ef 1 L 1 |Ii, , Q 2 mi � L 2 |I, m � |If, mf � E Time dependence gives access to splitting of hyperfine levels Most versatile of techniques at ISOLDE: Metals to proteins

PAC Elements produced at ISOLDE low energies & high multipolarities highly converted cascades e-g PAC e-g RED g-g PAC BLUE g-e PAC e-e

Multiferroic manganites AMn. O 3 Perovskite phases octahedra Van Aken , thesis univ. Groningen Hexagonal phase Trigonal bipyramid

Charge ordered manganites New scenario for the Charge Ordered State Theoretical work predicts the possibility of local electric dipole moments in CO manganites = + Site centred CO Inversion symmetry is broken Bond centred CO D. Efremov et al, Nature Materials, 3, 853 (2004) J. Van den Brink, D. I. Khomskii, J. Phys. Cond. Matt 20, 434217 (2008) Ferroelectricity due to Charge Ordering in Pr 1 -x. Cax. Mn. O 3 New paradigm for ferroelectrics, but it has been hard to prove experimentally that electric polarization exists in CO Pr 1 -x. Cax. Mn. O 3 (due to finite conductivity)

Local Probe Studies / Pr 1 -x. Cax. Mn. O 3 system Results: Electric susceptibility / spontaneous polarization below TC x=0. 35 ->TEDO=206 K, x=0. 4 ->TEDO=218 K, x=0. 85 -> TEDO=112 K Described as first-order dielectric phase transition below Tco A. M. L. Lopes et al. , Phys. Rev. Lett. 100, 155702 (2008)

Mössbauer spectrsocopy at ISOLDE: 57 Mn

Radioactive Mössbauer spectroscopy: other possibilities • Work with dilutions (< 10 -4 at. %) not possible with conventional MS • Site selective doping with different parents: 57 Mn (1. 5 m) 57 Fe 57 Co (271 d) Use in home laboratories 119 In PAC 119 m. Sn (290 d) (2. 1 m) 119 Sb 119 Sn (38 h) Off-line at ISOLDE Make use of special properties - Recoil to create interstitials (57 Mn, 119 In) - Observe meta-stable electronic states (57 Co)

Studies of “Magnetic semiconductors” Doping Zn. O semiconductors with few percentages of 3 d metals make the material magnetic at room temperature (Dietl et al. , Science, 287 (2000) 1019) Potential multifunction material or Dilute Magnetic Semiconductor (DMS) with applications in spintronics

Hyperfine interactions at the 57 Fe nuclear sites δ Δ δ 0 chemical bond oxidation state local symmetry local magnetic field (valence electrons, lattice)

Hyperfine interactions at the 57 Fe nuclear sites Δ δ δ 0 H Mössbauer sextet means magnetism at the Fe site

Mössbauer spectrum of 57 Fe in Zn. O Ferromagnetism vs. slow paramagnetism Defects vs. Fermi level effect [Weyer et al. , 2007]

Some recent results • Don’t have to worry about precipitation, implantations are low concentration • Can distinguish between paramagnetism and ferromagnetism • Can measure spin-lattice relaxation rates • Submitted to APL (2010)

Future Directions ØOnline emission channelling: lattice location in Semiconductors ØOnline diffusion ØBeta – NMR as applied to biophysics

Online Lattice location studies

Can probe isotopes with short half-lives: e. g. 27 Mg 61 Co Can address some important questions, e. g. role of Mg in Ga. N Properties of Co in materials such as Zn. O and Ga. N b- emission channeling patterns from 61 Co in Ga. N 61 Co on substitutional Ga sites

Beta-NMR applied to biophysics Beta-NMR Cu, Zn, Mg, Mn, Fe, Ni Measurement of electric field gradient Cu(I) is “invisible” in most (except X-ray and nuclear) spectroscopic techniques because it is a closed shell ion Cu(I)/Cu(II) are essential in many redox processes and electron transport in biology

Radioactive Tracers 600 isotopes, 68 68 elements 600 t 1/2 > 2 d 1 h < t 1/2 < 2 d current Plasma ion source Surface ionization (+/-) t 1/2 < 1 Laser h ionization future/current

ce Furna Detector Sputter-source lator u p i n Ma Beamport Tape station

Summary: Solid state physics at ISOLDE covers a wide range of materials and areas: Ø Semiconductors: • Si, Ge, Si. Ge, diamond, • III-V, nitrides, II-VI, Zn. O… • Electrical doping, transition metals, rare earths, H, • Diluted magnetic semiconductors Ø High-Tc superconductors and perovskites Ø Magnetism (manganites, CMR) Ø Biophysics… proteins, DNA, in vivo experiments Ø Low dimensional systems: Ø Surfaces, interfaces, multilayers Opportunities for Actinide Materials?

Multiferroic materials • Inversion symmetry breaking (charge-orbital related) • Dislocated spin density waves • Magneto-electric coupling Tb/YMn 2 O 5 Nature, 429, 392 (2004) Nature Materials 3, 164, (2004) Magnetic field induces a sign reversal of the electric polarization