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