Reprinted from the November 2000 edition of the Mössbauer Spectroscopy Newsletter, published as part of Volume 23, Issue 9 of the Mössbauer Effect Reference and Data Journal
In the response to a general call for information on the current Mössbauer research that is taking place in the United Kingdom and Ireland, the following reports were received by the Mössbauer Effect Data Center. Of particular note is the heavy emphasis on the use of Mössbauer spectroscopy to investigate chemical systems.
School of Chemistry
University of Bath
Bath – England
Names and Titles of Researchers
Academic Staff – Dr. K. C. Molloy
Postdoctoral Staff – Dr. M. Venter
Postdoctoral Staff – Dr. G. A. Horley
Graduate Student – M. C. Barret
Graduate Student – A. T. Kana
Graduate Student – L. Apostolico
Areas of Research
The group at the University of Bath is primarily interested in the chemistry of tin, and Mössbauer spectroscopy plays an important part of compound characterization. The majority of work concerns the synthesis of precursors for the MOCVD of thin films. Target films relevant to the use of Mössbauer spectroscopy include F-doped SnO2, tin sulfides, and tin phosphides. The group is also interested in the supramolecular chemistry of organotin compounds, for example the layer and channel structures adopted by organotin tetrazoles.
Department of Physics
University of Liverpool
Liverpool – England
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Names and Titles of Researchers Academic Staff – Dr. Michael F. Thomas Academic Staff – Dr. Dominic P. E. Dickson Research Student – G. Simon Case Research Student – Gabby H. Milford Research Student – John Bland Visiting Scientist – Sylvana Stewart (La Plata, Argentina – visiting Open University, UK) Visiting Scientist – Monica Calderaru (Romanian Academy of Sciences, Bucharest) Visiting Scientist – Tamara Tkachenka (Academy of Science, Minsk, Belarus) |
 L-R: Gabby Milford, Simon Case, Mike Thomas, Peter Normile (a fellow researcher in the Department), John Bland |
Areas of Research
Current Mössbauer studies at Liverpool are focusing on topics in magnetic multilayers, magnetic nanoparticles, magnetic oxides, catalysts, and systems with off-center atoms.
A major and continuing topic has been the study of magnetic anisotropy in metallic multilayers. Highlights of this work were reported at ICAME99. The work is continuing by studying rare-earth/iron systems that show strong anisotropies. An extensive study has been made of Ce/Fe and Ce/Fe0.49Co0.49V0.02 multilayers. Thin films and multilayers of Laves Phases DyFe2 and YFe2 are currently being investigated, and a variety of nanoparticle systems, recording media, oxide particles in ferrofluids, and the protein ferritin have been studied recently. Magnetic oxide studies include Fe3O4 both in bulk and in films of less than 10 monolayers as Fe3O4/Pt(111).
The group has collaborated with visiting scientists in investigations of the magnetism of CuO via samples of Cu(Fe57)O prepared by different methods, the action of Sb2O3/SnO2 catalysts followed by Sb121 and Sn119 Mössbauer spectroscopy, and the study of off-center atoms in the semiconductor Pb0.8Sn0.2Te0.8Se0.2.
Department of Physics and Astronomy
University College London
London – England
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L-R: Quentin Pankhurst, Louise Affleck, Andrew Steer, Daniel Ucko
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Names and Titles of Researchers
Dr. Quentin A. Pankhurst
Ph.D. Student – Louise Affleck
Ph.D. Student – Marco Aguas
Ph.D. Student – Quang Bui
Ph.D. Student – Seung-Jae Lee
Ph.D. Student – Daniel Morrison
Ph.D. Student – Andrew Steer
Ph.D. Student – Daniel Ucko
Areas of Research
Quentin Pankhurst and co-workers at University College London synthesize, characterize, and seek to understand a variety of technologically relevant new materials, including:
amorphous alloy nanoparticles for low-loss transformer cores
low-cost ferrite magnets for domestic and automotive applications
gold-on-metal oxide catalysts for carbon monoxide removal
fine-scale granular alloys for magnetic recording read/write heads
bio-compatible magnetic fluids for protein purification
soft and hard magnets in dentistry
Current research projects include the following:
SHS ferrites. The "fireworks" method of synthesizing both hard and soft ferrites. The novelty here is conducting the reaction in an applied magnetic field that results in a faster and hotter combustion wave, and alters the intrinsic coercivity and magnetization of the post-SHS powdered and sintered product. In experiments in fields up to 20 T the group also sees signs of field-dependent lattice parameter changes.
Chemical synthesis of amorphous alloys. Chemical precipitation of fine particle nanocrystalline or amorphous alloys under both aerobic and anaerobic conditions. Potential for the production of (i) bulk material which may be more easily used in applications than melt-spun ribbons, and (ii) otherwise inaccessible compositions. Some of the Fe-Zr-B alloys have promising soft magnetic properties.
Biocompatible supports. Magnetic separation using fine particle iron oxides coated with synthetic dyes to capture specified biochemicals. These materials offer a one-step protein purification process, compared to the 10 steps used in conventional liquid chromatography.
muSR studies of superparamagnetism. Studies of superparamagnetism in nanoscale granular alloys and fine particle magnetic oxides from a hitherto largely unexplored vantage point – muon spectroscopy. Experiments have been performed at ISIS near Oxford, and at PSI near Zürich.
Automotive catalysts. Low temperature CO oxidation using Au nanoparticle catalysts dispersed on porous metal oxide supports. These are high-activity catalysts that light up near 100 C compared to 400 C in conventional Pd-based catalysts. Focus on Au Mössbauer studies using facilities in Munich.
Magnets in orthodontics. Designing combinations of hard and soft magnets to achieve tooth movement without archwires. This has potential as a less invasive orthodontic treatment than is current practice.
Anisotropy in amorphous alloys. Fundamental studies of "moment canting" in soft magnetic Fe-Si-B ribbons – a phenomenon where even very large fields of 20 T or more cannot saturate the Fe magnetic moments. Scope for further work at DRAL on the x-ray and neutron scattering, and polarized Mössbauer studies.
Computer modeling of nanomagnetism. Computer-based modeling of the dynamical behavior of small magnetic particles in fluid suspensions – as used in areas ranging from magnetic inks to biochemical separation systems. Understanding the stability of the suspensions, and the tendency of the magnetic particles to coagulate, is especially important.
The group’s magnetic materials work involves close collaborations with people in other departments in University College London – Chemistry, Biochemical Engineering, Chemical Engineering, and Dentistry – and with members of laboratories in Spain, Germany, and Russia.
Department of Chemistry
The Open University
Milton Keynes – England
Names and Titles of Researchers
Head of Department – Prof. Frank J. Berry
Visiting Research Fellow – Dr. Silvana Stewart
Visiting Research Fellow – Dr. Hisham Widatallah
PhD Student – Ibrar Ayub
Ph.D. Student – Fred Vetel
Ph.D. Student – Louisa Knightley
Areas of Research
The synthesis and characterization of a wide range of ferrites by a number of methods is currently in progress. This includes the preparation of lithium- and rare earth-containing materials by hydrothermal processing and mechanical milling. Structural characterization by X-ray- and neutron diffraction compliments studies of local order by synchrotron EXAFS experiments. Mössbauer spectroscopy is needed to examine local structure, magnetic properties, and the redox proportion of the materials.
The group is also involved in studies of catalytically active materials, including zeolites, mixed oxides, and metallic catalysts. Studies of natural materials, especially meteorites, are conducted in collaboration with the Planetary Science Research Group.
Department of Biological Chemistry
John Innes Centre
Norwich – England
Names and Titles of Researchers
Project Leader – Dr. David J. Evans
Research Scientist – J. Elaine Barclay
Student – Matt Smith
Areas of Research
The enzymes nitrogenase and hydrogenase perform extremely important reactions in nature – nitrogen fixation and hydrogen-proton interconversion, respectively. The active sites of both enzymes are complex metallo-sulfur units that contain iron together with other metals. The group's program is to chemically synthesize structural and functional analogues of these active sites to help understand better the biological processes and to generate novel biomimetic catalysts. 57Fe-Mössbauer spectroscopy is an invaluable tool used in the characterization of the materials the group generates and iron coordination compounds prepared by other groups in collaboration. The group has performed also fundamental studies on those properties of iron-sulfur clusters that influence their Mössbauer parameters, and have extended and improved the reliability of the list of partial values for low-spin, octahedral, iron(II) complexes. During its studies the group has reported, to the best of its knowledge, the largest quadrupole splitting (4.55 mms-1 at 77 K) observed for high-spin iron(II) from the central, distorted tetrahedral, iron atom in the complex [Fe3(SC6H2iPr3-2,4,6)4{N(SiMe3)2}2].
Physics Department
Trinity College
Dublin – Ireland
Names and Titles of Researchers
Director – Prof. J. M. D. Coey
Research Fellow – M. Venkatesan
Areas of Research
Studies of electronic structure and magnetism of ferromagnetic oxides, especially half-metallic ferromagnets
Studies of magnetism of high-moment alloys prepared by electrodeposition
Iron in soils and silicate minerals
Permanent magnet materials
Glasgow Caledonian University
Glasgow – Scotland
Names and Titles of Researchers
Prof. M. El-Sharif
Prof. C. U. Chisholm
Prof. A. Vértes
Prof. E. Kuzmann
Student – Olivia Doyle
Student – Ian Brooke
Student – Jingli Yang
Collaborative Research between Glasgow Caledonian University and Eötvös Loránd University, Hungary
Since 1986 the research team (principal investigators – Prof. Colin U. Chisholm and Prof. Mahmoud El-Sharif) at Glasgow Caledonian University, Glasgow, UK (GCU) has collaborated with the research team (principal investigators – Prof. Ernô Kuzmann and Prof. Atilla Vértes) at Eötvös University, Budapest, Hungary (ELTE). This has involved a study of the mechanism of alloy deposition and Mössbauer analysis of the electrodeposited alloys. The research team at GCU has been studying the process parameters controlling the deposition and the research team at ELTE has been completing Mössbauer analysis on the resulting alloys. One study has entirely complemented the other, forming the basis of an ideal collaboration. Since the electrodeposited Fe-Ni-Cr alloys prepared by a new plating method developed at GCU were found to be microcrystalline and/or amorphous, Mössbauer spectroscopy has proven to be an excellent, sensitive, and unique tool to get detailed information about the phase composition, the short range order, and the magnetic structure of these electrodeposits and also about the structural changes due to aging and radiation effects. The collaborative research has resulted in about 34 scientific publications in international journals and conferences.
It was shown in the early work of this collaboration that the main phase of the thick electroformed Fe-Cr-Ni microcrystalline samples is ferromagnetic, which is contrary to the thermally prepared alloys of the same composition. In order to elucidate the origin and conditions of this metastable magnetic phase formation and the magnetic behavior of electrodeposited Fe-Ni-Cr alloys, comparative studies have been carried out on analogous systems (having similar composition range) prepared by other non-equilibrium methods, like physical vapor deposition of multilayers and energetic heavy ion irradiation (ion beam mixing) or laser beam irradiation, and the ball milling of alloys. The existence of a highly disordered microcrystalline ferromagnetic phase (which never occur in thermally prepared alloys) and its metastability have been shown in Fe-Cr-Ni alloys as dominant phase applying not only to electrochemical deposition, but ion-beam mixing of multilayers and ball milling preparation. Mössbauer spectroscopy was recognized as a sensitive analytical method to study the metastable phases in FeNiCr alloys prepared by non-equilibrium methods. In these collaborative investigations Prof. G. Principi (Padova University, Padova, Italy), Prof. Laszlo Takacs (Maryland University, Baltimore, USA), Prof. Vijayendra K. Garg (University of Brasilia, Brasilia, Brazil), Dr. Fatima Chibirova (Kharpov Institute, Moscow, Russia), and Prof. Kiyoshi Nomura (University Tokyo, Tokyo, Japan) have also participated. In order to establish an even more concerted common activity, the collaborating partners funded Surface Technology International, a center covering joint research and doctoral-level training, in 1997 at Budapest.
The collaboration program from 1986 to the present has covered many alloy systems, including Cr-Ni-Fe, Cr-Ni-Fe-P, Cr-Co, Cr-Sn, Fe-Co-Sn, and Zn-Sn. The published results have significantly extended and provided original knowledge in the field of alloy electrodeposition through Mössbauer analysis.
The cooperation between the research groups of GCU and ELTE is very successful. The partners often meet and visit each other. Prof. Atilla Vértes was given an honorary degree by GCU in 1995. Prof. Mahmoud El-Sharif is a Visiting Professor at ELTE, while Prof. Ernô Kuzmann is a Visiting Professor at GCU.
European Centre in Surface Engineering
The research groups are also currently leading a proposal for the establishment of an interdisciplinary European Centre in Surface Engineering (ECSE), which will bring together 10 complementary university laboratories from the UK and Europe. Once established, the ECSE will conduct joint research programs in the development of environmentally safe production technologies for coated, lined, or surface treated materials. The Centre will also provide industry, particularly those small companies which do not themselves have the necessary resources, with a low-risk route for materials research and development.