K S Krishnan Memorial Lecture

Speaker : Professor GA Gehring
Department of Physics and Astronomy, University of Sheffield
Topic : Magnetically doped ZnO: Is it a 'Dilute Magnetic Semiconductor'?
Date : December 12, 2007
Time : 11:30 AM
Venue : C V Raman Hall, IACS

All are cordially invited to attend.

Abstract: There is much activity world wide to find a good room-temperature dilute magnetic semiconductor because of the possibility of integrating logic and memory functions. ZnO, and other oxides, TiO2, In2O3, SnO2, (LaSr)TiO3, show weak ferromagnetism at room temperature when doped with small (<10%) concentrations of transition metal ions.

This lecture will explain the basic ideas of magnetic semiconductors and concentrate on the various physical measurements that may be made, electrical resistance, Hall effect, magneto-resistance, magneto-optics as well as studies of the magnetisation. There has been much controversy over whether the effects in the oxides are intrinsic to the bulk material or are due to surface states. A big question mark has hung over the question of the extent to which there are spin polarised mobile carriers as well as localised moments on magnetic ions.

Many of the reported oxide semiconductors were almost insulating and it has not been possible to observe a spin polarised current injected into other materials. A recent development has been the observation of ferromagnetic behaviour in samples that are also metallic. Magneto-optical data suggests that these materials have strongly polarised conduction bands and thus these materials do offer real possibilities for spintronics