Alistair Campbell joined the Group in 1996 after completing his B.Sc. in Physics at Birmingham University.
He began working on the magnetic, and structural properties of manganese oxide materials. In his second year he extended his work to include the study of the magnetic borocarbide superconductors
Alistair now works as a National Manager, (Product & Technology) for Giesecke and Devrient Australasia in Melbourne, Australia.
Ph.D. thesis summary
Neutron scattering has been used to study the colossal magnetoresistance manganite La0.835Sr0.165MnO3 and the magnetic superconductors HoNi2B2C and ErNi2B2C.
La1-xSrxMnO3 exhibits structural and magnetic phase transitions as a function of temperature. The temperature at which these transitions takes place has been use to show that in La1-xSrxMnO3 it is possible to induce a structural phase transition at constant temperature by the application of a magnetic field. At the temperature at which this field transition takes place, removal of the applied field does not produce a switch back to original structure. This confirms that in this doping regime the magnetic, electronic and structural properties of this material are strongly coupled.
HoNi2B2C and ErNi2B2C are magnetic superconductors that both exhibit metamagnetic phase transitions as a function of applied magnetic field at low temperatures. Neutron diffraction has been used to determine the magnetic phase diagram of HoNi2B2C in the plane of temperature and magnetic field, for two different orientations of a single crystal relative to the applied magnetic field. Two orientations have also been investigated for ErNi2B2C although the complete phase diagram has only been established for one orientation. The magnetic modulations in the different phases have been measured. The results for HoNi2B2C are compared with a simple theoretical model for the magnetic structure.
Publications resulting from Ph.D. work
Single-Crystal Neutron-Diffraction Study of a Structural Phase Transition Induced by a Magnetic Field in La1-xSrxMnO3 , A. J. Campbell, G. Balakrishnan, M. R. Lees, D. M. Paul, G. J. McIntyre, Physical Review B-Condensed Matter 55, R8622 (1997).