Applications of Mössbauer Spectroscopy at WITS and ISOLDE/CERN by Professor Deena Naidoo Wits-NECSA Workshop 09-10 September 2015

Applications of Mössbauer Spectroscopy Applications of Mössbauer Spectroscopy

at at

WITS and ISOLDE/CERNWITS and ISOLDE/CERN

by by

Professor Deena NaidooProfessor Deena Naidoo

Wits-NECSA Workshop 09-10 September 2015Wits-NECSA Workshop 09-10 September 2015

Outline of Presentation

Mössbauer Isotopes/Approaches

Measurables

WITS Mössbauer Facility and applications

Mössbauer at ISOLDE and applications

Local and International Collaborations

WITS-NECSA Workshop, South Africa, 09-10 September 2015

Mössbauer Isotopes


5757Fe Mössbauer SpectroscopyFe Mössbauer Spectroscopy

4WITS-NECSA Workshop, South Africa, 09-10 September 2015

Comparison of different MS Approaches

Mössbauer Approaches


Hyperfine Interactions and Measurables

Electric Monopole InteractionValence/spin state => Position of resonance lines.

Electric Quadrupole Interaction Site symmetry => Splitting of lines.


Hyperfine Interactions and Measurables

Magnetic interactions Zeeman splitting into 6-line pattern.

Other Measurables Spin relaxation rates (sextet broadening). Diffusion on a atomic scale (line broadening). Interaction with defects (implantation

damage/lattice sites). Debye temperature (resonance area/intensity).


Be Window

Mössbauer Facility @ WITS


Transmission MS

CEMS

Some Electronics

Some Research Samples

•Fly-ash•Multiferroics•Milled carbides with binders•Cemented carbides•Catalysts•Carbon nanomaterials•Rock bearing samples

Be Window

Apllications: WITS – Fly Ash


Be Window

Applications: WITS – Cemented Carbides


00-048-1816 (*) - Cobalt Iron - Co3Fe7 - Y: 13.76 % - d x by: 1. - WL: 1.78897 - Cubic - a 2.86340 - b 2.86340 - c 2.86340 - alpha 90.000 - beta 90.000 - gamma 90.000 - Primitive - Pm-3m (221) - 23.4772 - F

03-065-8828 (C) - Tungsten Carbide - WC - Y: 47.27 % - d x by: 1. - WL: 1.78897 - Hexagonal - a 2.90200 - b 2.90200 - c 2.83800 - alpha 90.000 - beta 90.000 - gamma 120.000 - Primitive - P-6m2 (187) - 1 -

Operations: Import

Sample 5 - File: d2_15_661.raw - Type: Locked Coupled - Start: 20.000 ° - End: 100.006 ° - Step: 0.026 ° - Step time: 37. s - Temp.: 25 °C (Room) - Time Started: 0 s - 2-Theta: 20.000 ° - Theta: 10.000 ° - Chi

Lin

(Cou

nts)

0

1000

2000

3000

4000

5000

6000

2-Theta - Scale

20 30 40 50 60 70 80 90 100

ISOLDE: Beam Production

Proton Booster Synchrotron

1 GeV p+

UC2 target

LaserSelective ionization of Mn and Sn

Accelerationto 60 keVImplantation

chamber

Mass separation

Mössbauer drive system and detector

• Proton induced fission in UC2 target Neutron rich isotopes • Laser Selective ionisation, Mn

• Electromagnet Mass selection (57Mn)

1.4

•Acceleration to 40 - 60 keV


On-line emission Mössbauer spectroscopy

57Mn decay to the 57Fe probe:

57Fe

57*Fe (τ = 140 ns) I = 3/2

I = 1/2

57Co (T½ = 271 days)57Mn (T½ = 85.4 sec.)

EC

-

Off-line

γ

14.4 keV Mössbauer transition

Ion-implantation of dilute dopants

into sample

Resonance detector

v

eenp


Be Window

Beamline(57Mn+ ions)

Implantation Chamber

Mössbauer Drive

Resonance Detector

To Electronics and data acquisition

Counting Gas

Mössbauer @ ISOLDE, CERN


Why Radioactive Beams (RIB)?

ISOLDEISOLDEOn-Line Isotope On-Line Isotope Mass SeparatorMass Separator

No problems with beam No problems with beam contamination.contamination.

Beam intensity (~2×108 57Mn/s).Total dose of ≤1012 57Mn/cm2. . 5757Mn Mn 5757mmFe (Fe (TT½½ = 1.5 min.) = 1.5 min.)

EERR ~ 40 eV. ~ 40 eV.

Study impurities Study impurities (~1016 atoms/cm3 <10<10-5 -5 at%).at%).High statistics spectrum (5 – 10 min).

Isothermal annealing studies on a Isothermal annealing studies on a timescale of minutes.timescale of minutes.Dose dependence. Measurements at different emission angles.

External magnetic field (Bext ≤ 0.6 T).Quenching


Some Research Samples

Diamond, SiC, GaN, AlN, InN, Si, Ge, Al2O3, MgO, ZnO (+ nanowires), TiO2, SnO2, GaAs, InP, GaP, FeV multilayers, Heusler Alloys, Topological insulators,

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

SiSiSi

Si

Si

Si

Si

Si

Si

Mn

Upon annealing of implantation damage (T > 450 K, t = 90 sec)

Mn enters predominantly substitutional sites or near-substitutional sites


Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

SiSiSi

Si

Si

Si

Si

Si

Si

Mn57*Fe

57Mn (T½ = 1.5 min.)

57*Fe 14.4 keV( = 140 ns)

-

<ER> = 40 eV

57Fe

eV 10~ 9

E

57Fe


Applications: ISOLDE - Silicon


Emission Channeling in Si @ ISOLDE

Four fractions:

• Random fraction (R) => disordered environment.• Ideal substitutional site (S)•Near substitutional site (near-S)•Near interstitial site (near-T)


Applications: ISOLDE - ZnO

D2D3

Bext

Bext

Velocity (mm/s)

Rel

ativ

e em

issi

on (

arb.

uni

ts)

(a)

(c)

(b)

Ion-implanted57Mn , c ~ 30°+

ZnO at 300 K

-12 -9 -6 -3 0 3 6 9 12

±1/2±3/2± 5/2

±1/2±3/2± 5/2

B ext= 0

c ~ 60°

B ext= 0.6 T║cθ ~ 60°

B ext= 0.6 T

Bext = 0 T: Complex magnetic sextet structure.

Magnetic structure originate from Kramers doublets.

• NO ordered magnetism. • Slow Relaxing Paramagnetism.


Some Collaborators at CERNSouth Africa: D. Naidoo, K. Bharuth-Ram, H. Masenda and M. Ncubeacknowledges support from South African National Research Foundation acknowledges support from South African National Research Foundation and the Department of Science and Technology.and the Department of Science and Technology.

Denmark: H.P. Gunnlaugsson, G. Weyer and M.B. Madsen.

Italy: R. Mantovan and M. Fanciulli acknowledges support from MIUR through the acknowledges support from MIUR through the FIRB Project RBAP115AYN “Oxides at the nanoscale: multifunctionality FIRB Project RBAP115AYN “Oxides at the nanoscale: multifunctionality and applications”.and applications”.

Iceland: T.E. Mølholt, S. Ólafsson and H. P. Gíslason acknowledges supportacknowledges supportfrom the Icelandic Research Fund.from the Icelandic Research Fund.

CERN-ISOLDE: K. Johnston

Belgium: G. Langouche

Germany: R. Sielemann


Local Collaboration

Professor D. Naidoo (Group Leader)Dr H. MasendaUndergraduate Students (Physics Majors III and

Materials Science III)Postgraduate Students (Honours, MSc and PhD)School of Physics: MPRI MembersModelling Group DST/NRF CoE in Strong MaterialsSchool of ChemistrySchool of GeosciencesUniversity of JohannesburgDurban University of Technology (DUT)MINTEK/ANGLO/CSIR/SASOL/ELEMENT 6NECSA – future?


Documents

Applications of Mössbauer Spectroscopy at WITS and ISOLDE/CERN by Professor Deena Naidoo Wits-NECSA Workshop 09-10 September 2015