¡¡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

Hyperfine Interactions of impurities

in solidsNanostructured

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 (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.

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 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. ErricoLic. G.N. DarribaMr. E.L. Muñoz (Diploma Thesis

student)

Structural, electronic, and magnetic properties in

doped systems:

first principles calculations and nanoscopic

experimental techniquesAims: *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. GiovanettiLic. 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

MagnetismDepartment 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. MizrahiGabriel A. Durán

Academic lines of research:Nanostructured iron oxide

particlesPhase transformations in alloysMagnetic properties of spinelsMagneto-resistive compounds

Shape-memory alloysHeterogeneous 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

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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.

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 SPECTROSCOPYTDPAC

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 111Cd, appropriated for PAC determinations, results from the disintegration of 111In by electron capture.

9/2+

111In

EC

7/2+ 0.12 ns17

1 keV

245

keV

85 ns

estable

5/2+

1/2+

2.83 d

111Cd

2

1

The PAC technique requires a radioactive isotope (probe)

9/2+

111In

EC

7/2+ 0.12 ns17

1 keV

245

keV

85 ns

estable

5/2+

1/2+

2.83 d

111Cd

2

1The 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 1964Uppsala,

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 N2 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.

)()2.40()8.12()66()16( 140140140140140 stableCehLadBasCssXe

140Xe was produced by 235U fission

140Ce is obtained via the - cascade

The magnetic Hyperfine field at 140Ce 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).

109Ag( , 2n)111In 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 111In/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:181HfAg:181Hf

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.

a R(t)

t (ns)

b R(t)

t (ns)

Martinez, 1981

0 2 4 6 8 10 12

2500

5000

7500

10000

12500

2res

= 0.7 ns

Núm

ero

de c

oinc

iden

cias

Tiempo (ns)

The ionic way:

R(t) spectra of 181Ta in K2ZrF6

NaI(Tl) (~ 3 ns)

CsF (~ 0,8 ns)

External War: Malvinas External War: Malvinas War (1982)War (1982)

Göttingen 19831986, Argentine won

the World Cup of football.

Conclusions:

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:

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

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