1. Department of Physics, University of the Western Cape, Private Bag X 17, Bellville 7535, South Africa
2. Highly Correlated Matter Research Group, Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa
3. Materials Research Group, iThemba LABS, P.O. Box 722, Somerset West 7129, South Africa
4. School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4001, South Africa
5. Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50 - 950 Wroclaw, Poland