¡¡Wellcome!!

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 Ferroelectric perovskites Applications of the Mössbauer Effect and Magnetism Physics of impurities in Condensed Matter Hyperfine Interactions of impurities in solids Magnetism and magnetic materials Nanostructured Materials

Dra. Cristina Caracoche Dr. Jorge Martinez Dr. Agustín Rodríguez Dra. Patricia Rivas Dra. Marcela Taylor Research group on Zirconia Ceramics Zirconia (ZrO2) 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.

Study of perovskites and aurivillius oxides. Dr. Alberto R. López García. Dr. Roberto Alonso. Dra. Marcela Taylor. Mr. Martín Falabella. Aim: Determine material’s 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 Sr1-xBaxHfO3, BaTi1-xHfxO3, Ca1-xSrxHfO3, SrTi1-xHfxO3, SrTi1-xHfxO3, CaTi1-xHfxO3 Bi4Srn-3HfxTin1-xO3n+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 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 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.

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 RN3M2005 Group of magnetic materials 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 SiO2/magnetic nanophase Isolators and transparent Low density magnets Magnetostriction sensors. Mössbauer Transmission Spectroscopy at fixed Doppler energies.

Nanostructured materials Aims: studies of *Nanostructured materials obtained by mechanical sinthesis. *Nanoestructured materials appropriated for hydrogen storage. *Complex magnetic structures. Dr. Luis A. Mendoza Zélis. Dra. Laura Damonte. Dr. Marcos Meyer. Lic. Lorena Baum. Ing. Christian Laborde Techniques: MÖSSBAUER SPECTROSCOPY TDPAC POSITRON ANNIHILATION SPECTROSCOPY (Dra. Laura Damonte)

Hyperfine Interactions of impurities in solids Aims: Studies of *Magnetism in thin oxide films, *Magnetism in intermetallic compounds, *Hydrogen in intermetallic compounds, *Hafnium-oxygen system, *Phase transitions in solids,... Dr. Alberto F. Pasquevich. Dra. Marcela Fernández van Raap Dr. Agustin M. Rodríguez. Technique: TDPAC

Perturbed Angular Correlation equipment of four detectors 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 PAC technique requires a radioactive isotope (probe) The isotope 111Cd, appropriated for PAC determinations, results from the disintegration of 111In by electron capture.

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 Prof. Dr Othaz La Plata, 1966 Dr. Othaz brough the electron-gamma spectrograph gifted for Uppasala University,Sweden. Prof. Dr Othaz La Plata, 1966

La Noche de los Bastones Largos 'the night of the long sticks' "the Night of long knifes." Beginning of the destruction of the education at Argentine Universities. 29 de julio de 1966 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 Anyway the Science was preserved

Years later, Prof. Sadosky said: We believed that, we were doing transcendental things that the society valorized, and discovered our isolation in the worst way. 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. This prompted the New York Times to publish a note on the incident, which gave international notoriety to the situation.

Times of the Civil War (1973-1976) 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 N2 but all know how looks the air.

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. The magnetic Hyperfine field at 140Ce in nickel. 140Xe was produced by 235U fission 140Ce is obtained via the - cascade

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).

Synchrocyclotron times: (1978-1983) 109Ag( , 2n)111In Alpha particles Natural silver foil Radiation damage Annealing or melting required E= 56 MeV Acknowledgments: M. Behar and G. García Bermúdez

Sincrociclotron times (Indium jailed in silver) Impurity-defect interactions Impurity -impurity interactions 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). Charge transfer model for quadrupole interactions and binding energies of point defects with 111In/Cd probes in cubic metals. Gary S. Collins and Matthew O. Zacate. Hyperfine Interactions (2004) Current times

1979 – Prof. Erwin Bodenstedt visits for second time La Plata. Impurity-defect interactions 1979 – Prof. Erwin Bodenstedt visits for second time La Plata. One month before Bibiloni brings two samples implanted in Bonn: Au:181Hf Ag:181Hf Radiation damage, e-- PAC Radiation damage, - PAC A.F. Pasquevich F. H. Sánchez

Times of Internal oxidation. Beginning with the impurity -impurity interaction project we accidentaly re-discovered the interaction between impurities and Oxygen in Silver. The important thing was that we were able to develope an onw research project. This discovery give us some international acknowledgement (not much, of course!). But we were in the herd. 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.

Splitting: Oxidized and Ionics. 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.

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.

The ionic way: CsF (~ 0,8 ns) R(t) spectra of 181Ta in K2ZrF6 Martinez, 1981 NaI(Tl) (~ 3 ns)

External War: Malvinas War (1982)

1986, Argentine won the World Cup of football. Göttingen 1983

Conclusions: …no nos fue tan mal!. The group grew and diversify. Originated at the Hyperfine field has now many projections in the Solid State Physics. …no nos fue tan mal!.

National network on magnetism and magnetic materials: RN3M2005 National network on magnetism and magnetic materials: LBT: LOW TEMPERATURE PHYSICS LAB. FCEyN - UBAires LAL: LASER ABLATION LAB., FI - UBAires LSA: AMORPHOUS SOLIDS LAB., FI - UBAires GSM: GROUP OF NANOSTRUCTURED MATERIALS MADE BY MECHANOSYNTHESIS, FCE - UNLPlata LAFMACEL: PHYSICAL CHEMISTRY OF CERAMIC ELECTRONIC MATERIALS LAB., FI - UBAires LEMöss: MÖSSBAUER SPECTROSCOPY LAB, CAC – CNEAbaires GMC: CONDENSED MATTER GROUP, CAC – CNEAbaires GMOxAl: GROUP OF MAGNETISM AND STRUCTURE IN OXIDES AND ALLOYS, FCE - UNLPlata HIIS: HYPERFINE INTERACTIONS AT IMPURITY SITES IN SOLIDS, FCE - UNLPlata GCM: MATERIALS SCIENCE GROUP, FAMAF - UNCORdoba LRM-CAB: MAGNETIC RESONANCE GROUP, CAB – CNEAbaires GTPEM: ELECTRONIC AND MAGNETIC PROPERTIES THEORY GROUP, CAC – CNEAbaires LAFISO: SOLID STATE LABORATORY FCyE - UNTucuman GMM: MAGNETIC MATERIALS GROUP, FCE - UNLPlata