Outline Current research lines. Brief history of the Group and the context in which it developed. Conclusions.
Who is who in the cake? In occasion of the 65 birthday of Alberto López García.
Current lines Zirconia Ceramics Hyperfine Interactions of impurities in solids Nanostructured Materials Applications of the Mössbauer Effect and Magnetism Ferroelectric perovskites Physics of impurities in Condensed Matter Magnetism and magnetic materials
Research group on Zirconia Ceramics Zirconia (ZrO 2 ) and zirconia based ceramic materials constitute a vast ensemble of compounds that can be efficiently investigated using the TDPAC technique. Aims: produce stabilized tetragonal and cubic zirconia based ceramics (powders, films, compacts, glassceramics, related compounds) and characterize the resulting materials at nanoscopic scale using the PAC and ME (in compounds containing Fe) techniques, as a function of temperature up to 1200C. A PAS equipment will be soon be active. Dra. Cristina Caracoche Dr. Jorge Martinez Dr. Agustín Rodríguez Dra. Patricia Rivas Dra. Marcela Taylor
Study of perovskites and aurivillius oxides. Dr. Alberto R. López García. Dr. Roberto Alonso. Dra. Marcela Taylor. Mr. Martín Falabella. Aim: Determine materials properties, some with ferroelectric characteristics, dependence on composition and temperature: calorimetric measurements, impedances as a function of frequency, crystalline and electronic structure, effects of impurities and defects, phase transitions, hyperfine electric field gradients, the change of bond types, etc. Simple calculations based on point charge model and on first principles theory are performed. Currently investigated materials Sr 1-x Ba x HfO 3, BaTi 1-x Hf x O 3, Ca 1-x Sr x HfO 3, SrTi 1-x Hf x O 3, SrTi 1-x Hf x O 3, CaTi 1-x Hf x O 3 Bi 4 Sr n-3 Hf x Tin 1-x O 3n+3 with n =3, 4 and x = 0.1, 0.2 x < 1
Physics of impurities in Condensed Matter Dr. A.Guillermo Bibiloni. Dr. M. Rentería (Coordinator ) Dr. L.A. Errico Lic. G.N. Darriba Mr. E.L. Muñoz (Diploma Thesis student) Structural, electronic, and magnetic properties in doped systems: first principles calculations and nanoscopic experimental techniques Aims: *EFG characterization and modeling at impurity sites in binary oxides. *Structural and electronic properties of doped semiconductors. *Dilute magnetic semiconductors (DMS): structural, electronic, and magnetic properties in magnetic- and nonmagnetic-impurity-doped oxide semiconductors. *Surfaces and clusters in (pure/defect/doped) oxide semiconductors. *Applications: Determination of nuclear-quadrupole moments (Q).
Physics of impurities in Condensed Matter Dr. A.Guillermo Bibiloni. Dr. Félix Requejo (Coordinator) Dr. José Ramallo López Lic. L. Giovanetti Lic. L. Andrini Synchrotron radiation techniques applies to nanostructured systems. *Catalysis. *Fundamental properties of nanoparticles. *Surfaces and interfaces.
Laboratory of Applications of the Mössbauer Effect and Magnetism Department of Physics, School of Exact Sciences, National University of La Plata Promote the academic excellence in the traditional fields of the School of Exact Sciences. Encourage interdisciplinary research activities, scientific extension and services in the area of the School. Bring up graduates able to work in trans-disciplinary groups, connected with the local scientific and technological necessities. Researchers: Roberto C. Mercader Judith Desimoni, Silvana J. Stewart, Sonia M. Cotes, Rodolfo A. Borzi, Electronic support: Luis D. Junciel Technical support: Flavio R. Sives PhD Students: Javier Martínez Martín D. Mizrahi Gabriel A. Durán
Academic lines of research: Nanostructured iron oxide particles Phase transformations in alloys Magnetic properties of spinels Magneto-resistive compounds Shape-memory alloys Heterogeneous supported catalysts and precursor systems. Applied and inter-disciplinary lines: Loess-paleosols sequences. Metallurgy. Clays, soils and iron-bearing minerals. Archaeology artifacts. Samples relevant to environmental science. Aim: dope the pores with Fe oxides to obtain nanotubes and nanowires. MCM-41 (Mobile Crystalline Material)
Group of magnetic materials RN3M 2005 Dr. Francisco Sánchez Dra. Marcela Fernández van Raap Dra. Fabiana Cabrera Dra. Claudia Rodríguez Torres Lic. Pedro Mendoza Zélis Lic. Gustavo Pasquevich National Network of Magnetisn and Magnetic Materials Magnetic aerogels SiO 2 /magnetic nanophase Isolators and transparent Low density magnets Magnetostriction sensors. Mössbauer Transmission Spectroscopy at fixed Doppler energies.
Dr. Luis A. Mendoza Zélis. Dra. Laura Damonte. Dr. Marcos Meyer. Lic. Lorena Baum. Ing. Christian Laborde Nanostructured materials Aims: studies of *Nanostructured materials obtained by mechanical sinthesis. *Nanoestructured materials appropriated for hydrogen storage. *Complex magnetic structures. Techniques: MÖSSBAUER SPECTROSCOPY TDPAC POSITRON ANNIHILATION SPECTROSCOPY (Dra. Laura Damonte)
Hyperfine Interactions of impurities in solids Dr. Alberto F. Pasquevich. Dra. Marcela Fernández van Raap Dr. Agustin M. Rodríguez. Aims: Studies of *Magnetism in thin oxide films, *Magnetism in intermetallic compounds, *Hydrogen in intermetallic compounds, *Hafnium-oxygen system, *Phase transitions in solids,... Technique: TDPAC
Perturbed Angular Correlation technique This technique is appropiated for detecting the hyperfine interactions at radioactive impurities (probes) sites. By Hyperfine Interactions we means the interactions of the probe nuclear spin with the surrounding. Perturbed Angular Correlation equipment of four detectors
The isotope 111 Cd, appropriated for PAC determinations, results from the disintegration of 111 In by electron capture. The PAC technique requires a radioactive isotope (probe)
The probability of detecting 2 at an angle from the direction of detection of 1 is measured as a function of the time t that the nucleus is in the intermediate state of the cascade.
La Plata, August 1964 Uppsala, 1966 La Plata, 1966 Prof. Dr Othaz Dr. Othaz brough the electron-gamma spectrograph gifted for Uppasala University,Sweden.
Beginning of the destruction of the education at Argentine Universities. Anyway the Science was preserved 29 de julio de 1966 "the Night of long knifes." La Noche de los Bastones Largos 'the night of the long sticks' Our Department of Physics results benefited. Well recognized theoretical physicists were incorporated. For the experimental physics at La Plata, the shortage of funds made necessary the use of personal resources (piccola cajeta) Ongania´s Time
Seeing what came later, with murders and missing people, we felt that we had been fortunate that night. The fact had transcendence because an USA mathematician (Prof. Warren Ambrose from the MIT) was among the attacked persons. We believed that, we were doing transcendental things that the society valorized, and discovered our isolation in the worst way. This prompted the New York Times to publish a note on the incident, which gave international notoriety to the situation. Years later, Prof. Sadosky said:
Those were difficult years but nobody could imagine what will come later. How to explain to control patrols and police barriers that such smoke substance was not explosive. The probability of overcoming was bigger if you talk about liquid Nitrogen than liquid air. The soldiers and policeman were very clever for discovering great liars. Most of them did not know what was the normal physic state of N 2 but all know how looks the air. Times of the Civil War (1973-1976)
The bloody dictatorship 1976 - 1983 The pencil's night September 1976 C. López Claro, argentine artist.
Time of IALE (Isotopes far from stability line) project. 140 Xe was produced by 235 U fission 140 Ce is obtained via the - cascade The magnetic Hyperfine field at 140 Ce in nickel.
Time of IALE (Isotopes far from stability line) project. Will they be on the front cover of the new TDPAC Herald?
"…something you could show or not, but remember that somebody could visit you to verify if it is still in your bookshelf…" 1980, flying to the SLAFES at Gramado (Brazil).
109 Ag(, 2n) 111 In Synchrocyclotron times: (1978-1983) Acknowledgments: M. Behar and G. García Bermúdez Alpha particles Natural silver foil Radiation damage Annealing or melting required E = 56 MeV
Dose-Rate Dependence of the Impurity-Defect Interaction in Silver. L. Thomé and H. Bernas. Phys. Rev. Lett. 36, 1055–1057 (1976) "TDPAC studies of radiation damage in AgPd and AgPt alloys" E. Bożek, K. Królas, B. Wodniecka, P. Wodniecki, Hyperfine Interactions 4 (1978) 689. K. Królas, B. Wodniecka, P. Wodniecki, "Interaction between impurities in Ag dilute alloys", Hyperfine Interactions 4 (1978) 605. Electric field gradients produced by impurity atoms in a cubic Ag lattice. F. C. Zawislak, R. P. Livi, L. Amaral, J. Schaf, and M. Behar. Hyperfine Interactions, 2, 242, (1976). Sincrociclotron times (Indium jailed in silver) Charge transfer model for quadrupole interactions and binding energies of point defects with 111 In/Cd probes in cubic metals. Gary S. Collins and Matthew O. Zacate. Hyperfine Interactions (2004) Current times Impurity-defect interactions Impurity -impurity interactions
1979 – Prof. Erwin Bodenstedt visits for second time La Plata. One month before Bibiloni brings two samples implanted in Bonn: Au: 181 Hf Ag: 181 Hf Impurity-defect interactions A.F. Pasquevich Radiation damage, - PAC Radiation damage, e - - PAC F. H. Sánchez
P. Wodniecki, B. Wodniecka, "TDPAC studies of internal AgIn alloy oxidation", Hyp. Int.12 (1982) 95. W. Bolse, H. Schröder, P. Wodniecki, M. Uhrmacher, "Innere Oxidation von Silber-Indium Legierungen", Deutsche Physik. Gesellschaft Konferenz, Münster 1982. Times of Internal oxidation. Beginning with the impurity -impurity interaction project we accidentaly re-discovered the interaction between impurities and Oxygen in Silver. This discovery give us some international acknowledgement (not much, of course!). But we were in the herd. The important thing was that we were able to develope an onw research project.
The internal oxidation project produces the first division of the group: The short lifetime of indium, conjugated with a manually driven two detectors equipment required day and night work, and some members of the lab, because familiar reasons could not work under such pressure. Splitting: Oxidized and Ionics.
The oxidized way: After all that, "aftereffects were coming". The study of PAC spectra of internal oxidized indium in silver, rise the idea of studying normal Indium oxide. Salomón et al.Bäverstram and Othaz model.
Martinez, 1981 The ionic way: R(t) spectra of 181 Ta in K 2 ZrF 6 NaI(Tl) (~ 3 ns) CsF (~ 0,8 ns)