Speaker
Prof.
Krishanlal Bharuth-Ram
(University of KwaZulu-Natal, South Africa)
Description
K. Bharuth-Ram 1, H. P. Gunnlaugson 2, T E Mølholt 3, D. Naidoo 4, R. Mantovan 5, H. Masenda 4, M. Ncube 4, K. Johnston 6, W. Dlamini 1, R. Sielemann 7, H. P. Gíslason 3, G.Langouche 8,S. Ólafsson 3, G. Weyer 2, and the ISOLDE Collaboration 6
1 School of Physics, University of KwaZulu-Natal, South Africa; 2 Institute of Physics and Astronomy, Aarhus University, Aarhus, Denmark; 3 Science Institute, University of Iceland, Reykjavík, Iceland; 4 School of Physics, University of the Witwatersrand, South Africa; 5 Laboratorio MDM IMM-CNR, Agrate Brianza (MB), Italy; 6 EP Division, ISOLDE/CERN, Switzerland; 7 Helmholtz Zentrum – Berlin, Germany; 8 Department of Physics, KU - Leuven, Leuven, Belgium.
Theoretical prediction of ferromagnetic behaviour above room temperature in ZnO (and GaN) doped with dilute concentrations (6 – 8%) of transition metal (TM) ions has excited considerable interest because of their potential as semiconductor-compatible magnetic components for spintronic applications. Observation of room temperature ferromagnetism (RTFM) in ZnO doped with TM ions have been reported, however, no clarity exists on the origin of the observed magnetism, which has been attributed to dopant-defect complexes, unintentional precipitation, or to the formation of secondary magnetic phases. The Mössbauer Collabo-ration at ISOLDE/CERN has applied 57Fe emission Mössbauer spectroscopy following the implantation of 57Mn*, to study the nature of the magnetism in ZnO and other metal oxides and III-nitrides. Radioactive beams of 57Mn+ (T½ = 1.5 min) ions are produced at the ISOLDE facility following fission in a UC2 target induced by 1.4 GeV protons and multi-stage element selective laser ionization. High purity beams of intensity of ~3×108 ions/s were implanted with 40-60 keV energy and to fluences below 1012 ions/cm2 into commercially available single crystal samples. The Mössbauer spectra obtained on-line after implantation into ZnO single crystals show magnetic hyperfine sextets originating from Fe in the high-spin Fe3+ state. Measurements in an external magnetic field show that these sextets are not due to ferromagnetic Fe but to paramagnetic substitutional Fe3+ with unusually long relaxation times. Similar high-spin Fe3+ paramagnetic sextet structure is also observed in MgO and alpha-Al2O3. Results obtained for ZnO, alpha-Al2O3 and MgO, as well as preliminary results for GaN, AlN and InN, will be presented.
| Presentation Type | Oral |
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Primary authors
Dr
Deena Naidoo
(University of the Witwatersrand, South Africa)
Prof.
Gerd Weyer
(University of Aarhus, Denmark)
Prof.
Guido Langouche
(KU-Leuven, Belgium)
Prof.
Haflidi Gíslason
(University of Iceland, Iceland)
Mr
Hilary Masenda
(University of the Witwatersrand, South Africa)
Dr
Karl Johnston
(Physics Division, ISOLDE, CERN, Geneva)
Prof.
Krishanlal Bharuth-Ram
(University of KwaZulu-Natal, South Africa)
Mr
Mehluli Ncube
(University of the Witwatersrand, South Africa)
Prof.
Palle Gunnlaugsson
(University of Aarhus, Denmark)
Dr
Rainer Sielemann
(Helmholtz Zentrum - Berlin, Germany)
Dr
Roberto Mantovan
(Laboratorio Nazionale MDM CNR-INFM, Italy)
Prof.
Sveinn Ólafsson
(University of Iceland, Iceland)
Mr
Torben Molholt
(University of Iceland, Iceland)
Ms
Wendy Dlamini
(Univesrity of KwaZulu-Natal, South Africa)
