Regional Groups of Mössbauer Researchers - Germany

Reprinted from the May 2002 edition of the Mössbauer Spectroscopy Newsletter, published as part of Volume 25, Issue 5 of the Mössbauer Effect Reference and Data Journal

Mössbauer Spectroscopy in Germany

In response to a general call for information on the current Mössbauer research that is taking place in Germany, the following reports were received by the Mössbauer Effect Data Center.

Physik-Department E 15
Technische Universität München

Prof. Fritz Wagner “with two of those dear old cryostats. They are some 35 years old, but still going strong.”
Dr. Ursel Wagner in her laboratory “with some of all those thousands of samples of ceramics.”

Names and Titles of Researchers

Prof. Dr. Friedrich E. Wagner
Dr. Ursul Wagner
Siegfried Haslbeck – Ph.D. Student
Gabriel Sieben – Diploma Student
Dr. Rupert Gebhard, Archaeological State Collection, München – Collaborator
Dr. Christoph Flügel, Bavarian Office for Non-Government Museums, München – Collaborator
Dr. Werner Häusler, Institute of Soil Science, Technische Universität München – Collaborator

Areas of Research

The on-going research of Prof. Wagner’s group at Physik-Department E15 is on a variety of subjects, but the main effort these days is on archaeometry, mainly studies of ancient ceramics from both southern Germany and Peru. This is mainly Dr. Ursul Wagner’s field. The Wagners have applied both neutron activation analysis (using the old Munich research reactor, which unfortunately was closed down in the summer of 2000) and Mössbauer spectroscopy, as well as thin section microscopy and X-ray diffraction, but the war horse of it all is 57Fe Mössbauer spectroscopy. They have run Mössbauer spectra of thousands of samples both at room temperature and 4.2 K and the data in the database in which all these things are bunkered will probably keep Fritz and Ursel Wagner busy for years after the last Mössbauer spectrometer has ceased to function.

Besides the archaeometry effort, Prof. Wagner has recently been doing work in a variety of fields and using such isotopes as 197Au, 193Ir, 99Ru, 151Eu, 121Sb, 119Sn, and, certainly, 57Fe. Subjects are gold chemistry, iridium chemistry, work on various types of catalysts, gold ruby glass and other types of silicate glasses, magnetic and other properties of various alloy systems, and gold ores. Since the old reactor, built in the middle of the 1950s and in fact the first research reactor in Germany, was closed down in the summer of 2000, isotopes like 197Au and 193Ir are not easy to do any more, since they need to have the sources irradiated at far away places, if at all. They are waiting for the new reactor, which is finished and sitting outside the window of Prof. Wagner’s office, waiting (for the past year and a half) for the permission of the government to switch it on.

Physik-Department E17
Technische Universität München

Names and Titles of Researchers

Prof. Dr. F. G. Parak – Group Leader
Dr. Klaus Achterhold – Scientist
Dr. Olga Iakovleva – Scientist
Simonetta Croci – Ph.D. Student
Walter Gutscher – Ph.D. Student

Areas of Research

Proteins are involved in nearly all facets of life. Their structure with different degrees of flexibility, as well as their structural changes, are decisive for biological function. Prof. Parak’s group is interested in the biophysics of proteins and applies a large number of different experimental techniques, such as X-ray and neutron crystallography, EPR, optical spectroscopy, etc. However, Mössbauer spectroscopy in the energy and the time domain has proven to be the crucial tool for the investigation of protein dynamics. Structural fluctuations and relaxation are studied, labeled by the iron centers in proteins. The oxygen-storing proteins myoglobin, mini-myoglobin, and neuro-myoglobin, as well as the oxygen transport protein hemoglobin, are still the center of interest. Further investigations are performed on different HiPIPs and cytochrome c, photosystem II, and reaction centers. The temperature dependence is used to separate protein-specific motions from the usual solid state behavior. In order to study the change of conformations, metastable states are produced by irradiation with X-rays or with light. To vary the properties of protein molecules, mutants are produced in their own gene laboratory. The classical Mössbauer absorption technique with 57Fe and the Rayleigh scattering of Mössbauer radiation with 57Fe and 183W are applied.

With nuclear forward scattering of synchrotron radiation, the group determines precise information about structural distributions, the solid-state dynamics, and protein-specific dynamics. Of high value is the Phonon Assisted Mössbauer Effect, which allows the determination of the phonon density of states at the iron site. By the inelastic scattering of synchrotron radiation with an energy analysis by the Mössbauer effect, the group obtains information about the dynamics of all atoms.

In the application of the Mössbauer effect the group cooperates with groups in Argonne, USA (Alp, Sturhahn); Grenoble, France (Rüffer, Chumakov); Hamburg, Germany (Gerdau, Shvyd’ko, Franz); Lübeck, Germany (Trautwein); Moscow, Russia (Frolov, Krupyanskii, Prusakov, Semin); and Parma, Italy (Ortalli).

Mössbauer Laboratory
Institut für Anorganische Chemie und Analytische Chemie
Johannes-Gutenberg Universität

Names of Researchers

Prof. (em.) Dr. Philipp Gütlich
Dr. Ashis Bhattacharjee
Dr. Jürgen Ensling
Dr. Shashank Kane
Dr. Göstar Klingelhöfer
Dr. Vadim Ksenofontov
Dr. Joachim Kusz
Dr. Sergey Reiman
Dr. Franz Renz
Dr. Ulrich Stumm
Dr. Petra van Koningsbruggen
Dr. habil. Hartmut Spiering
Bodo Bernhardt
Stefanie Berinskat
Victor Chameko
Karlheinz Häuser
Gabriele Lehr
Daniel Rodionov
Christian Schröder

Description and Areas of Research

The Mössbauer group at Mainz, under the direction of Prof. (em.) Dr. Philipp Gütlich, has always been comprised of both chemists and physicists – the synthesis of spin crossover materials, physical characterization on a sophisticated level, and interpretation of data on theoretical grounds within the parameters of one group has been a very successful strategy. The group is composed of 15 scientific researchers, including doctoral students, postdoctoral researchers, and guests from all over the world. Although Mössbauer spectroscopy is the main technique (with approximately 10 spectrometers), the group also employs other techniques for studies of electronic structure and physical properties of transition metal compounds.

The scientific activities of the group concentrate on three main objectives: (a) spin crossover – thermally, pressure, light induced (→LIESST); (b) aftereffects of the nuclear decay of 57Co doped transition metal compounds →NIESST; and (c) corrosion and surface investigations. Also of interest are exchange coupling effects in dinuclear and polynuclear transition metal complexes, mixed valence compounds, and molecular magnets. The spin crossover project has long been investigated by the Mainz group, and nearly 150 publications on this subject have been contributed.

The University of Mainz’s Mössbauer laboratory is perhaps one of the world’s best-equipped laboratories for physical inorganic chemistry research, including Mössbauer spectroscopy for transmission, scattering, time-dependent, and depth-selective measurements, under pressure, applied magnetic fields and laser excitation; UV-vis, Raman, and FTIR spectroscopy; magnetometers for magnetic measurements; a microcalorimeter for heat capacity measurements; and X-ray diffractometers. Mainz is one of the very few places where 61Ni Mössbauer experiments are possible due to the presence of accelerator facilities (MAMI). All methods are set up for variable temperature measurements, most of them down to the liquid helium range. In some cases temperatures of up to 1000 K are possible. Specialized equipment includes:

  • Several Mössbauer spectrometers for routine measurements.

  • Combination ESCA/AUGER/Mössbauer spectrometer for surface studies. The apparatus is also set up for Depth-Selective Conversion Electron Mössbauer Spectroscopy (DCEMS). Problems of interest: phase analysis of iron-containing thin layers (e.g., Langmuir-Blodgett layers), corrosion of steel, and leaching of glasses.

  • Mössbauer spectrometer used for 61Ni measurements at temperatures down to 4.2 K and in external magnetic field. The source 61Co(t1/2=99 min) in 62Ni0.85Cr0.15 is activated in an 800 MeV electron accelerator. Samples of interest are size and direction of local magnetic fields in nickel spinel compounds and High Tc-superconductors, nickel compounds with unusual valence states.

  • Mössbauer coincidence spectrometer for time-differential Mössbauer emission spectroscopy of 57Co-labeled insulating systems at variable temperatures down to 4.2 K. The time resolution is ca. 3.5 ns in the time regime ca. 5-500 ns. One hundred twenty-four spectra are recorded simultaneously. Problems of interest: physical and chemical aftereffects of 57Co(EC)57Fe decay, such as “Nuclear Decay-Induced Excited Spin State Trapping” (NIESST Effect) in transition metal compounds.

  • Vibrating sample magnetometer (FONER type) and SQUID magnetometer for magnetic susceptibility measurements at variable temperatures down to ca. 2 K, also under applied hydrostatic pressure (up to ca. 15 kbar). Problems of interest: iron(II) compounds exhibiting thermal- and optical-induced spin transition, molecular magnetism, valence tautomerism in cobalt compounds.

  • Resonance Raman spectrometer for studies of vibrational spectra at variable temperatures (down to 4.2 K). The set-up is equipped with several lasers (Argon, Krypton, and Ti-sapphire). Problems of interest: vibrational properties of transition metal compounds exhibiting dynamical electron structures (spin crossover, valence tautomerism).

  • FT-FIR-spectrometer for temperature dependent investigations of vibrational properties in the range ca. 10-3000 cm-1 (with additional extension up to ca. 30.000 cm-1). The apparatus is particularly suited for LIESST effect studies (Light-Induced Excited Spin State Trapping) on iron(II) compounds exhibiting thermal and optical switching properties.

Institut für Physik
Medizinische Universität zu Lübeck

Names and Titles of Researchers

Prof. Dr. Alfred X. Trautwein – Director
Prof. Dr. Ventzislav Rusanov – Guest Professor
Dr. Hauke Paulsen – Scientist and Lecturer
Dr. Volker Schünemann – Scientist and Lecturer
Dr. Heiner Winkler – Scientist and Lecturer
Dr. Olga Zakharieva – Scientist
Dr. Frederic Averseng – Postdoctoral Research Associate
Dr. Lee Reilly – Postdoctoral Research Associate
Rüdiger Benda – Ph.D. Candidate
Svetoslav Stankov – Ph.D. Candidate
Thomas Teschner – Ph.D. Candidate
Patrick Wegner – Ph.D. Candidate

Areas of Research

  • Application of molecular orbital calculations (local density and ab initio methods) to the determination of electronic structures and molecular properties. The group’s applications deal with molecules and clusters that contain mono- or polynuclear metal centers and are therefore also accessible to spectroscopic studies of the metal centers.

  • Structure-function relationships in metallopro-teins and -enzymes. The group investigates by means of Mössbauer, EPR, XANES, and EXAFS spectroscopy as well as SQUID magnetometry metalloproteins and -enzymes and corresponding model compounds to gain insight into the mechanisms of their functionalities. Of special interest are the active centers of iron-sulfur proteins (Rieske centers, anaerobic ribonucleotide reductases, biotin synthases), iron-oxygen proteins (aerobic ribonucleotide reductases, methane monooxygenases) and heme proteins (peroxidases, cytochrome P450, myoglobin, NO-carrying heme proteins from the saliva of blood sucking insects).

  • Polynuclear spin-coupled systems. The group investigates the paramagnetizm of spin-coupled subunits in polynuclear biomolecules or model complexes spectroscopically as well as quantum theoretically with respect to its mixed valency, spin-spin or spin-lattice relaxation, exchange or double-exchange interaction. The intention of these studies is to understand relations between steric structures and molecular electronic and magnetic properties and to promote the “molecular design” of biomimetic metal centers.

  • Molecular switches. Spin-crossover complexes of transition metals have the ability to be switchable back and forth between two spin states by temperature, pressure, or light. This property opens the possibility to design molecular switches. In the framework of an international cooperation, the group investigates spin-crossover complexes of various composition, in particular such with long-lived light-induced metastable spin states. The group has extended its studies also to various kinds of nitroprussiates where the NO ligand can assume three different conformations induced by irradiation with light.

  • Nuclear resonant scattering of synchrotron radiation. Since it is also possible to use nuclear elastic forward scattering (NFS) of synchrotron radiation for Mössbauer spectroscopy in the time domain, the group makes use of the advantages of this method, i.e., the time structure, the polarization and the brilliance of the radiation, in some of its studies. By means of nuclear inelastic scattering (NIS) it is possible to investigate in the energy range of 0 to 150 meV those molecular vibrational modes in which the iron ion takes part. The group studies in particular spin-crossover complexes, nitroprussiates [Fe(CN)5NO]2-, and biomimetic model compounds by NIS and compare the results with a theoretical normal-mode analysis.

Laboratorium für Angewandte Physik
Gerhard-Mercator University Duisburg

Names and Titles of Researchers

Dr. Werner Keune – Professor
Richard A. Brand, Ph.D. – Staff
Balaram Sahoo – Ph.D. Student
Ellen Schuster – Ph.D. Student
Jürgen Voss – Ph.D. Student
Marco Walterfang – Ph.D. Student
Robert Peters– M.S. Student
Frank Stromberg – M.S. Student
Alexei Chrenov – Student

Areas of Research

The Mössbauer group at the University of Duisburg is currently working in the following areas:

  • Preparation of magnetic thin films and multilayers and silicide films by vacuum deposition and molecular beam epitaxy and their characterization by surface analytical techniques (AES, LEED, RHEED), X-ray diffraction, and AFM.

  • Depth-selective conversion electron Mössbauer spectroscopy (DCEMS) for surface phase analysis after ion implantation of 57Fe into Si.

  • Interface magnetism by conversion electron Mössbauer spectroscopy of 57Fe probe layers at Fe/semiconductor interfaces.

  • Structure and magnetism of alloy thin film with perpendicular magnetic anisotropy on semiconductor substrates.

  • Spin structure determination by conversion electron Mössbauer spectroscopy in ferromagnetic/antiferromagnetic layered systems with exchange-bias properties.

  • Vibrational dynamics of layered systems using nuclear resonance inelastic X-ray scattering (NRIXS) of synchrotron radiation.

  • Structure and vibrational dynamics of quasicrystals using a multi-technique approach by employing Mössbauer spectroscopy, EXAFS, synchrotron X-ray and neutron scattering (elastic and inelastic), and nuclear resonance inelastic X-ray scattering (NRIXS) of synchrotron radiation.

  • Phase analysis of chemically prepared alloy nanoparticles by Mössbauer spectroscopy.

Mössbauer Spectroscopy Group
Institut für Physikalische und Theoretische Chemie
Technische Universität Braunschweig

From Left (Back): M. Menzel, D. E. Mack, Dr. V. Sepelak,
Prof. K. D. Becker; (Front): O. Bartels, A. Constantinescu
Names and Titles of Researchers

Prof. Dr. Klaus D. Becker
O. Bartels, Dipl.-Chem. –
Ph.D. Student
A. Constantinescu, Dipl.-Chem. – Ph.D. Student
M. Kreye, Dipl.-Chem. –
Ph.D. Student
D.E. Mack, Dipl.-Phys. –
Ph.D. Student
M. Menzel, Dipl.-Chem. –
Ph.D. Student
Dr. V. Sepelak – Visiting Scientist

Areas of Research

  • Solid state processes at high temperatures. Perovskites and perovskite-related compounds are studied by in situ measurements at high temperatures to obtain insight into the charge states, the distribution of iron ions on inequivalent lattice sites, and on the structural phase stability. Measurements up to 1400°C have been conducted on the systems Sr-Fe-Co-O and Sr-La-Fe-O, and on Ca and Mn doped YFeO3 at defined oxygen partial pressures. The kinetics of the formation reactions of iron carbides (Fe3C) and iron nitrides (Fe4N, ε-Fe3N) have been studied in time-resolved experiments as a function of component activities and temperature.

  • Structure and chemical properties of glasses. Sn Mössbauer spectroscopy of tin-doped calcia-, sodium-, and alumina-containing borate and silicate glasses provides information on the structural and chemical character of SnII and SnIV ions in the various glass matrices.

  • Mechanochemical reactions in ferrite spinels. Investigations of homogeneous as well as of heterogeneous solid state reactions brought about by high-energy milling of spinels like MgFe2O4, NiFe2O4, and ZnFe2O4: changes in the cation distributions; and redox processes and formation reactions. Low-temperature Mössbauer spectroscopy of the nanoscale spinels in an external magnetic field on local coordination, oxidation state, and the magnetic states (superparamagnetism, collective magnetic excitations, etc.). The thermal stability range of the nonequilibrium cation distributions and of the canted spin arrangements in the nanocrystalline strained oxides is determined by high-temperature Mössbauer spectroscopy.

Other Items of Interest

The group will organize the 4th International Conference on Mechanochemistry and Mechanical Alloying (4th INCOME) in Braunschweig, Germany, from September 7-11, 2003. There will be a special session on Mössbauer spectroscopy in mechanochemistry.

Mössbauer Spectroscopy Group
Institut für Metallphysik und Nukleare Festkörperphysik
Technische Universität Braunschweig

Prof. Dr. Jürgen Hesse
Dr. Heiko Bremers
Oliver Michele
Oliver Hupe

Names and Titles of Researchers

Prof. Dr. Jürgen Hesse – Director of the Institute
Dr. Heiko Bremers – Scientist
Oliver Hupe – Scientific Collaborator Performing His Thesis
Oliver Michele – Scientific Collaborator Performing His Thesis

History and Areas of Research

The Mössbauer effect spectroscopy work of Prof. Hesse’s group started in 1972 and therefore introduced this powerful method at the Technische Universität Braunschweig. The topics of research are magnetic properties of metallic systems, like transition metal alloys with exotic spin structures (spin glasses, re-entrant ferromagnetism), nanostructured systems, and small particle behavior. Mössbauer spectrometry is a very valuable tool that the group always uses in combination with other experimental techniques, such as magnetization or susceptibility measurements, and in collaboration with electron microscopy or neutron spin depolarization.

In the very beginning the group started with Fe-Cr alloys and earned unresolved 57Fe Mössbauer six-line spectra. This led them to the idea of hyperfine field distributions, which together with Window’s paper has become very popular since that time. Later, the group turned its attention to the Invar problem, investigating Fe-Ni, Fe-Pd, and Fe-Pt alloys, to re-entrant spin glasses as Fe-Ni-Mn and Fe-Al-Mn, searching for objective criteria to find relaxation effects, to nanostructured alloys like Fe-Cu-Nb-Si-B or Fe-Cu-Nb-B, and to single domain nanosized particles like iron, etc. Along the way the group also discussed the possibilities of measuring the vector nature of the hyperfine field applying polarized Mössbauer sources and absorbers. Concerning nanoparticles embedded in a ferromagnetic amorphous matrix, Mössbauer spectroscopy in radio frequency magnetic fields became attractive. The first results the group performed together with Prof. Michal Kopcewicz in his laboratory in Warsaw and discovered the partial collapse effect. Together with Prof. Alexander Afanas’ev and Dr. Mikhail Chuev, this problem successfully was attacked from the theoretical viewpoint. Now the group is working on nanoparticles and recently applied Afanas’ev’s and Chuev’s very new idea of the extended two level relaxation model to fit spectral components exhibiting relaxation behavior in their spectra on nanosized Fe-Cu-Nb-B alloys. One of the group’s members (Dr. Bremers) has started to become familiar with the Mössbauer effect with synchrotron radiation.

II. Institut für Experimentalphysik
Universität Hamburg

From Left: E. Gerdau, M. Lerche, M. Lucht, H.-C. Wille, H.-D. Rüter, Yu.V. Shvyd’ko

Names and Titles of Researchers

Prof. Dr. E. Gerdau – Group Leader
Dr. H. D. Rüter – Senior Scientist
Dr. Y. Shvyd’ko – Senior Scientist
M. Lucht – Ph.D. Student
H.-C. Wille – Ph.D. Student
M. Lerche – Ph.D. Student

History and Areas of Research

The group opened the field of nuclear resonant scattering of synchrotron radiation in 1984. This was the first step towards the realization of an X-ray resonator. In 1997, the group succeeded in observing exact backscattering of resonant quanta with high efficiency and thus performed a needed second step for the realization of an X-ray resonator, for example of the Fabry-Perot type. The actual work of the group follows three lines:

1. Demonstration of applications of exact backscattering:

  • Precision determination of the wavelengths of nuclear resonant transitions.

  • Introduction of the precise wavelength of nuclear transitions as a length standard in the Angström region.

  • Precision determination of lattice constants (for example, in crystals of different isotopes).

2. Experimental realization of an X-ray Fabry-Perot resonator.

3. Development of efficient detectors for the observation of nuclear resonant scattering in the energy regime of 50 - 100 keV.

Further information can be found on the group Web page at http://www.rrz.uni-hamburg.de/hfww/gruppe.html.

Mössbauer Group
II. Physikalisches Institut
Universität Göttingen

Left to Right: Ulrich Vetter, Katarina Sedlackova, Peter Schaaf, Ettore Carpene, Michael Kahle, Alexander Müller

Names and Titles of Researchers

Prof. Dr. Peter Schaaf – Head of the Group, Professor of Physics
Ettore Carpene, Dipl.Phys. – Ph.D. Student (Soon to Be Postdoctoral Scientist)
Michael Kahle, Dipl.Phys. – Ph.D. Student
Alexander Müller, Dipl.Phys. – Ph.D. Student
Ulrich Vetter, Dipl.Phys. – Ph.D. Student
Prof. Dr. Marcel Miglierini – Visiting Professor
Dr. Ratnesh Gupta – Visiting Scientist
Dr. Sankar Dhar – Visiting Scientist
Katarina Sedlackova, Dipl.Phys. – Guest Ph.D. Student
Emily Hooker – Visiting Student

Areas of Research

Concerning Mössbauer spectroscopy, the group is performing 57Fe and 151Eu Mössbauer spectroscopy and operating four spectrometers. More often than the conventional transmission geometry (TMS), the group is performing conversion electron and conversion X-ray Mössbauer spectroscopy (CEMS and CXMS). Due to the group’s special detector set-up, they can measure all these three spectra simultaneously (STRMS). At the moment they can only measure at room temperature, but they are now trying to install also low temperature facilities.

Besides Mössbauer spectroscopy the group regularly uses X-ray diffraction, ion-beam analysis (RBS – Rutherford backscattering spectroscopy, RNRA – resonant nuclear reaction analysis, and channeling), perturbed angular correlation (PAC), nanoindentation hardness measurements, magneto-optical Kerr effect (MOKE), EXAFS, and surface profiling. Additional methods sometimes used are PL/CL, STM, AFM, MFM, SEM, TEM, and XPS.

Laser surface treatment is the main research topic. Laser nitriding and laser carbiding are extensively investigated by the group. If iron and steel is treated in such a way, Mössbauer spectroscopy is the appropriate tool for the surface phase analysis. Many publications have arisen from these investigations. Besides this reactive incorporation of nitrogen and carbon, the structural changes in amorphous or nanocrystalline alloys are also investigated. Bulk glasses have also been measured. Furthermore, the interaction of layered systems (bilayers, multilayers) with energetic ion beams are investigated, e.g., ion beam mixing of Fe/Si bilayers with the aim of producing the optoelectronic material beta-FeSi2. Phase analysis is mainly performed by CEMS.

Recently, the investigation of magnetic textures in ferromagnetic films induced by ion- or laser-beam was also brought into the group’s research interests. A novel development of Mössbauer spectroscopy is used for the analysis of the spin structure. They are also newly investigating thin films of cubic boron nitride (c-BN) as well as tetrahedral amorphous carbon (ta-C) doped with 151Eu. The films are grown by mass selected ion beam deposition under ultrahigh vacuum conditions. Current doping concentrations of 151Eu are chosen in the range of 0.1 %. Besides in situ characterization of the thin films, the group uses 151Eu-CEMS for ex situ analysis.

The group is involved in the European Training and Mobility program via the ERASMUS network: http://www.ph2.physik.uni-goettingen.de/NFP/feedback.htm.

More details can be found at the group’s Web site at http://www.uni-goettingen.de/~pschaaf. The Web page includes a list of publications, with on-line access to most.

Hahn-Meitner Institut

Names and Titles of Researchers

Dr. Rainer Sielemann – Head of Group
Dr. M. Mueller – Postdoctoral Scientist (terminated March 2002)
Dr. R. Govindaraj – Visiting Postdoctoral Scientist (terminated December 2001)
Dipl. Physiker L. Stadler – Student (terminated 2001)

Areas of Research

The group at the Hahn-Meitner Institut presently focuses on the physics of defects in semiconductors by employing radioactive probes in a wide sense. “Radioactive probes” includes radioactivity for Mössbauer spectroscopy, perturbed angular correlation (PAC), and special methods in semiconductor physics, such as DLTS (Deep Level Transient Spectroscopy), then called R-DLTS (Radiotracer-DLTS).

Mössbauer spectroscopy (mostly emission s.) presently is resting upon 119Sn fed by various parent activities: 119Sb, 119gTe, and 119mTe. All of these parent activities can be produced and implanted at will by utilizing the ISL heavy ion accelerator at the Institut and yield parent-specific physics in a semiconductor. The semiconductor materials researched include elemental Ge and GeSi, as well as the compound materials InSb, GaSb, and CdTe. In the past (up to 1998), the group had a strong research program on defect and diffusion physics studied by the "In-beam Mössbauer spectroscopy" technique on Coulomb excited 57Fe.

The personnel listed above have been working in Mössbauer spectroscopy; presently Dr. Sielemann’s group is partly changing research direction to synchrotron radiation, but will stay in Mössbauer spectroscopy partly in the semiconductor field and probably also in magnetism of thin films and interfaces. New collaborators will (hopefully) shortly be engaged for Mössbauer spectroscopy.

Mössbauer Group
Bayerisches Geoinstitut
Universität Bayreuth

Names and Titles of Researchers

Dr. Catherine McCammon – Staff Scientist
Dr. Leonid Dubrovinsky – Staff Scientist
Prof. Friedrich Seifert – Professor

Areas of Research

Mössbauer studies at Bayerisches Geoinstitut (BGI) focus on the physical and chemical properties of minerals as they relate to the structure, composition, and dynamics of the Earth’s interior, and can be divided into three main areas:

  1. Crystal chemistry of minerals. These include studies of site distribution, phase transformations, Fe3+/Fe2+ determination, magnetic properties, and lattice dynamics. Nearly every mantle high-pressure phase can be synthesized in the BGI high-pressure facility and examined ex situ using Mössbauer spectroscopy. The spectrometers have temperature capabilities from 1.5 to 1000 K at atmospheric pressure.

  2. Diamond anvil cell studies. In situ high-pressure studies in the BGI laboratory include phase transformations, chemical reactions, and changes in electronic structure with pressure. Current equipment includes a range of diamond anvil cells with capabilities over one megabar, with possibilities for both heating and cooling, complemented by a state-of-the-art laser heating facility.

  3. Mössbauer milliprobe. A simple technique for collecting Mössbauer spectra on microscopic samples was developed at BGI, and is currently used to study a wide variety of samples, including inclusions in diamonds, zoned minerals, glass-crystal assemblages, meteorites, and rare minerals.

II. Physikalisches Institut
Universität zu Köln

Names and Titles of Researchers

Prof. Dr. Mohsen Abd-Elmeguid – Group Leader
Prof. Dr. Hans Micklitz – Group Leader
Dr. Jochen Plessel
Dr. Bingfan Ni
Roman Lengsdorf

Areas of Research

The figure on the left shows two types of pressure set-up. The large one (B4C or sintered diamonds) is used especially for 170Yb and 151Eu Mössbauer spectroscopy (ME) up to 30 GPa. The small one (diamond anvil cell: DAC) is used for 57Fe, 119Sn, and 151Eu ME. The figure on the right shows the inner part of the DAC. The wires are used for measuring the electrical resistance under high pressure on the same sample.

The main research activity of the group at the University of Cologne is the investigation of the effect of pressure on the magnetic, electronic, and structural properties in systems with strongly correlated 3d, 4f, and 5f electrons. Such systems for example include Fe-based magnetic oxides, Eu(Fe,Co)2P2, Yb-based Kondo-lattices systems, and U(In1-xSnx)3. The group uses both conventional Mössbauer spectroscopy (57Fe, 119Sn, 151Eu, and 170Yb) and the nuclear resonance scattering of synchrotron radiation (57Fe, 119Sn, and 151Eu) at the European Synchrotron Radiation Facility in Grenoble.

High-pressure experiments can be performed up to 100 GPa using B4C, sintered diamond, and diamond anvil cells in a temperature range between 350 mK and 350 K and in an external magnetic field up to 10 T.

Mössbauer Group
Institute for Transuranium Elements
European Commission, Joint Research Centre

Jean Rebizant

Eric Colineau

Names and Titles of Researchers

Jean Rebizant – Deputy Head of Unit
Eric Colineau

Areas of Research

The central objective of basic actinide research in ITU and in its numerous collaborations worldwide is the elucidation of the electronic structure of actinide metals and actinide compounds. The dualism between localized and itinerant character of 5f electrons is a key problem in these studies. Actinide elements are radiotoxic and reactive; their preparation, handling, and measurement require a high level of security and a heavy infrastructure. Mössbauer spectroscopy is a powerful and suitable tool to investigate the local magnetic and electronic properties of actinide compounds. In particular, it is not sensitive to the encapsulation, nor to eventual non-resonant impurities. The group at ITU uses the 237Np resonance (5/2-5/2, E = 60 keV, source: 241Am, T1/2 = 458 y), the most popular in the actinides, and operates three spectrometers, down to T = 1.5 K and up to P = 10 GPa. Recent studies include Np2T3X4 and Np2T2X families, NpxSiy and NpxGey binaries and U-Np mixed dioxides.

In the frame of the ITU "User Lab," external scientists from the European Union and associated countries are welcome to submit proposals and conduct their own experiments with our technical, scientific, and financial support.

Institut für Ionenstrahlphysik und Materialforschung
Forschungszentrum Rossendorf e.V.

Dr. Helfried Reuther

Names and Titles of Researchers

Dr. Helfried Reuther – Scientist
Dr. Maximilian Dobler – Former Ph.D. Student (now with Leica Microsystems)

Areas of Research

At Forschungszentrum Rossendorf, Mössbauer spectroscopy is mainly used for analysis of phase formation after ion implantation. In the past, many systems were investigated by conversion electron Mössbauer spectroscopy: iron (and partly steel) implanted with nitrogen, carbon, boron, phosphorus, alumium, silicon ions and silicon, aluminum, and magnesium implanted with iron ions. Conventional transmission Mössbauer spectroscopy is used to determine the oxidation state of iron in different minerals.

Universität Paderborn

Prof. Dr. Gerhard Wortmann
Hubertus Giefers

Names and Titles of Researchers

Prof. Dr. Gerhard Wortmann – Group Leader
Dipl.-Phys. Kirsten Rupprecht – Ph.D. Student
Dipl.-Phys. Hubertus Giefers – Ph.D. Student

Description and Areas of Research

Paderborn is an old town of about 120,000 inhabitants, founded around the year 800, and has a 30-years’-young University. The Mössbauer activities are found within the Physics Department in a high-pressure research group involved in solid-state spectroscopy and materials science. The Mössbauer effect with radioactive sources, but now increasingly nuclear resonance scattering (NRS) of synchrotron radiation, is used, as well as other synchrotron-based methods such as XRD and X-ray absorption spectroscopies (XANES, EXAFS, XMCD).

For normal Mössbauer spectroscopy, the group uses the 57Fe (14.4 keV), the 151Eu (21.6 keV), and the 155Gd (86.5 keV) resonances. They can apply pressures up to 100 GPa (1 Mbar) with diamond-anvil cells and can vary, in addition, the temperature between 2 K and 700 K. Other options are a high-temperature oven and external magnetic fields. The group’s NRS activities are concentrated on the two Mössbauer beamlines of the European Synchrotron Radiation Facility (Grenoble) and, in some cases, on the beamline 3ID at the Advanced Photon Source (Argonne). The group developed special diamond-anvil cell for nuclear forward scattering (NFS) and nuclear inelastic scattering (NIS). In the last years the group has studied with NFS the band magnetism in RFe2 Laves phases and the Heisenberg magnetism in high-pressure phases of EuS and EuTe as well as valence and high-spin/low-spin transitions. The most emphasis has been laid on phonon spectroscopy under high pressure; the group performed the first high-pressure NIS studies of iron in the α-phase and ε-phase up to 42 GPa. These studies were continued, together with American colleagues, to pressures of 150 GPa. They used also the texture in ε-Fe to study phonon spectra as seen parallel and perpendicular to the hexagonal c-axis. Presently, the phonon spectra of the classical Invar systems Fe65Ni35 are studied at pressures up to 17 GPa, where the Invar properties have disappeared. Other activities of the group are presented on its Web site at the University of Paderborn (www.uni-paderborn.de).

Bundesanstalt für Materialforschung und -prüfung
Zweiggelände Berlin-Adlershof

Name and Title of Researcher

Dr. Michael Menzel – Scientific Collaborator

Areas of Research

Dr. Menzel is working on characterization of Sn- and Fe-phases in inorganic and organic substances and compounds such as glasses, steel, alloys, minerals, catalysts, corrosion products, zeolites, and building materials by Mössbauer spectroscopy.

If financial means become available, one to two visiting scientists are in the BAM lab for some months each year. Dr. Menzel offers the possibility of practical training for one student.

Hamburger Synchrotronstrahlungslabor (HASYLAB)
Deutsches Elektronen-Synchrotron (DESY)

Names and Titles of Researchers

Hermann Franz – Beamline Scientist
Karel Saksl – Postdoctoral Scientist
Gerd Wellenreuther – Ph.D. Student
Kirill Messel – Ph.D. Student (currently at the Kurchatov Institute, Moscow)
Anita Ehnes – Beamline Engineer

Areas of Research

The group at HASYLAB is running the undulator beamline at the PETRA II storage ring. The group’s main scientific topics concern dynamics in amorphous systems and iron alloys. In particular, they are studying anharmonicities reflected in the phonon density of states in the vicinity of solid-solid phase transitions in FePt and FeNi alloys. The properties of amorphous systems are characterized both in the region of fast (nuclear inelastic scattering) and slow (quasielastic nuclear resonant forward scattering) dynamics. Again, features at the onset of the "phase-transition" (glass-liquid crossover) are in the focus of the group’s interest. In recent experiments they studied the behavior of model systems under extreme conditions, i.e., high pressure and geometrical confinement. Most of the work is done in close collaboration with the group at the Technische Universität München (U. van Bürck) and T. Asthalter from Universität Stuttgart.

Aussenstelle Marktredwitz
Bayerisches Geologisches Landesamt

Names and Titles of Researchers

Dr. Enver Murad – Director, External Section

Areas of Research

Jerry Bigham of The Ohio State University at an AMD site.

The Bayerisches Geologisches Landesamt (Geological Survey of Bavaria) at present does not possess Mössbauer spectrometers of its own. During the past decade most Mössbauer work was carried out in cooperation with the Physics Department of the Technical University of Munich (E15) and the Physics Department of Monash University (Melbourne, Australia).

Mössbauer work carried out at the Bayerisches Geologisches Landesamt has been concerned mainly with minerals that form in the weathering environment and their reactions upon heating or other treatments. Much of this work has addressed clay-sized phyllosilicates (clay minerals sensu stricto) and natural clays of complex composition, and the reactions of these materials upon heating; most of these studies have been carried out in cooperation with Ursel Wagner at the Physics Department (E15) of the Technical University of Munich. Another group of materials that has been studied in detail are the precipitates that form in highly acid environments when sulfides contained in coals or metallic ores are oxidized upon exposure to the ambient atmosphere ("acid mine drainage precipitates," AMD); many of these studies have been carried out in cooperation with Jerry Bigham at the School of Natural Resources at The Ohio State University.

Mössbauer Group
Universität Rostock

Left to Right: Ralf Röhlsberger, Torsten Klein, David Mate del Rincon (kneeling), Radu Nicula, Stephan Flor, Klaus Quast, and Stefan Otto

Names and Titles of Researchers

Dr. Ralf Röhlsberger – Group Leader
Dr. Eberhard Burkel – Head of Department
Radu Nicula – Postdoctoral Scientist
Klaus Quast – Postdoctoral Scientist
Torsten Klein – Graduate Student
David Mate del Rincon – Graduate Student
Kai Schlage – Graduate Student
Stefan Otto – Student
Stephan Flor – Technician

Areas of Research

The main subject of the Rostock Mössbauer group is nuclear resonant scattering (NRS) of synchrotron radiation. In this field they work in the following areas:

  • Magnetism and lattice dynamics of thin films, surfaces, and nanostructures. Due to the outstanding brilliance of modern synchrotron radiation sources, the group is able to probe magnetic properties with monolayer sensitivity.

  • Development of new scattering methods (lighthouse effect, inelastic scattering). The nuclear lighthouse effect has the potential to perform NRS experiments in previously inaccessible areas (e.g., high transition energies, picosecond time resolution).

The group runs two sputtering machines for preparation of magnetic thin films. X-ray diffractometry, transmission electron microscopy, magneto-optics, and conventional Mössbauer spectroscopy (transmission and CEMS) are used for characterization of the samples. In close collaboration with the groups of Prof. K. H. Meiwes Broer and J. Bansmann at Universität Rostock, the group investigates the magnetic properties of clusters and size-selected nanoparticles.

On a regular basis the group performs experiments at the nuclear resonance beamlines of HASYLAB at DESY (Hamburg, Germany), ESRF (Grenoble, France), and APS (Argonne, USA).

Institut für Anorganische und Analytische Chemie
Universität Freiburg

Name and Title of Researcher

Prof. Dr. Christoph Janiak

Areas of Research

Prof. Janiak’s research interests include:

  • Supramolecular inorganic coordination chemistry; ambidentate, multidentate nitrogen donor ligands; construction of polynuclear complexes and coordination polymers; porous structures; weak interactions and collective phenomena in the solid state

  • Poly- and oligomerization of olefins with metallocene and other homogeneous molecular/single-site catalysts; Ziegler-Natta catalysis; olefin metathesis

This site is supervised by Mössbauer Effect Data Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China. Contact email: medc@dicp.ac.cn