Speaker
Mr
Hilary Masenda
(School of Physics, University of the Witwatersrand, Johannesburg, 2050, South Africa)
Description
III-Nitrides doped with 3d metals have attracted much attention since the theoretical prediction that Mn-doped GaN is a potential dilute magnetic semiconductors with high Curie temperatures (Tc ≥ 300 K), resulting from carrier mediated magnetic interactions due to itinerant holes coupling with localized dopant spins. Several reports have shown these materials to exhibit different forms of magnetism, the origin of which is still under debate.
We have undertaken emission 57Fe Mössbauer spectroscopy measurements on GaN, AlN and InN films after implantation of radioactive 57Mn+ ions at ISOLDE/CERN. The samples were held at temperatures between 105–726 K in an implantation chamber and implanted with 57Mn fluences up to 10^12 ions/cm^2. Spectra were collected at gamma emission angles of 0 degrees and 60 degrees relative to the sample's c-axis.
The spectra obtained for GaN and AlN reveal magnetic structure in the ‘wings’ of the spectra which were analysed using a semi-empirical relaxation model utilizing two Blume-Tjon (BT) sextets. The observed magnetic effect may be explained by a slow spin-lattice relaxation due to paramagnetic substitutional Fe3+ weakly coupled to the lattice. The observed spin-relaxation rate closely follows a T2 temperature dependence, characteristic of a Raman process. On the other hand, the spectra for InN did not reveal any presence of magnetic features; this could be explained by the absence of high spin Fe3+.
The central region of the spectra for all samples showed angular dependence and was initially fitted with two quadrupole split doublets assigned to Fe atoms on substitutional III sublattice (FeS) and the majority of Fe located on or near substitutional sites associated with vacancy type defects (FeC). In addition, a third quadrupole split doublet (FeD) was required to give good fits. The absence of anisotropy on (FeD) suggest that this component is due to Fe atoms in isolated amorphous zones.
The annealing behaviour and variation of hyperfine parameters for the fitted spectral components in these materials will be presented.
Primary author
Mr
Hilary Masenda
(School of Physics, University of the Witwatersrand, Johannesburg, 2050, South Africa)
Co-authors
Dr
Deena Naidoo
(School of Physics, University of the Witwatersrand, Johannesburg, 2050, South Africa)
Prof.
Gerd Weyer
(Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark)
Prof.
Guido Langouche
(Instituut voor Kern-en Stralings fysika, University of Leuven, 3001 Leuven, Belgium)
Prof.
Hafliði P. Gíslason
(Science Institute, University of Iceland, Dunhaga 3,107 Reykjavík, Iceland)
Prof.
Haraldur P. Gunnlaugsson
(Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark)
Dr
Karl Johnston
(PH Dept, ISOLDE/CERN, 1211 Geneva 23, Switzerland)
Prof.
Krish Bharuth-Ram
(School of Physics, Durban University of Technology, Durban 4000, South Africa)
Mr
Mehluli Ncube
(School of Physics, University of the Witwatersrand, Johannesburg, 2050, South Africa)
Dr
Roberto Mantovan
(Laboratorio MDM, IMM-CNR, Via Olivetti 2, 20864 Agrate Brianza (MB), Italy)
Prof.
Sveinn Ólafsson
(Science Institute, University of Iceland, Dunhaga 3,107 Reykjavík, Iceland)
Dr
Torben Mølholt
(Science Institute, University of Iceland, Dunhaga 3,107 Reykjavík, Iceland)
