Post on 03-Jan-2016
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
5757Fe Mössbauer SpectroscopyFe Mössbauer Spectroscopy
4WITS-NECSA Workshop, South Africa, 09-10 September 2015
Comparison of different MS Approaches
Mössbauer Approaches
WITS-NECSA Workshop, South Africa, 09-10 September 2015
Hyperfine Interactions and Measurables
Electric Monopole InteractionValence/spin state => Position of resonance lines.
Electric Quadrupole Interaction Site symmetry => Splitting of lines.
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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).
WITS-NECSA Workshop, South Africa, 09-10 September 2015
Be Window
Mössbauer Facility @ WITS
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
Be Window
Applications: WITS – Cemented Carbides
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
Be Window
Beamline(57Mn+ ions)
Implantation Chamber
Mössbauer Drive
Resonance Detector
To Electronics and data acquisition
Counting Gas
Mössbauer @ ISOLDE, CERN
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
Applications: ISOLDE - Silicon
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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)
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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.
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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
WITS-NECSA Workshop, South Africa, 09-10 September 2015
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?
WITS-NECSA Workshop, South Africa, 09-10 September 2015