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SUMMARY:Theory of exchange splittings of bands in diluted magnetic semicon
 ductors - Prof. Dr. Thomas Dietl\, Institute of Physics\, Polish Academy o
 f Sciences\, and Institute of Physics\, University of Warsaw
DTSTART:20091119T141500Z
DTEND:20091119T151500Z
UID:TALK19127@talks.cam.ac.uk
CONTACT:Dr Jonathan Keeling
DESCRIPTION:Giant magneto-optical and magneto-transport effects specific t
 o diluted magnetic semiconductors as well as carrier-mediated ferromagneti
 sm in these systems are known to originate from the presence of a sizable 
 spin-dependent coupling between effective mass carriers and electrons loca
 lised on the open d shells of transition metal impurities. A series of rec
 ent photoemission and magneto-optical experiments\, particularly on magnet
 ically doped nitrides and oxides\, but also on (Ga\,Mn)As\, points to our 
 limiting understanding of the physics governing the sp-d exchange interact
 ions in diluted magnetic semiconductors. \n\nI will present a revisited th
 eory of magneto-optical effects in diluted magnetic semiconductors[1] and 
 show that it explains the unexpected antiferromagnetic sign of the apparen
 t s-d exchange coupling found for photoelectrons in (Ga\,Mn)As[2] and the 
 apparent ferromagnetic p-d exchange interaction reveled by magnetooptical 
 studies for (Zn\,Co)O\, (Ga\,Mn)N\, and (Ga\,Fe)N[3] as well as\, a long t
 ime ago\, for (Ga\,Mn)As on the insulator side of the metal-to-insulator t
 ransition[4]. \n\nThese findings have important consequences on ferromagne
 tism in these systems and help to understand the evolution of the Curie te
 mperature on going from arsenides to phosphides and to nitrides containing
  a few percent of randomly distributed Mn ions. \n\n\nfn1. C. Śliwa\, T. 
 Dietl\, _Phys. Rev. B_ *78*\, 165205 (2008)\;  T. Dietl\, _Phys. Rev. B_ *
 77*\, 085208 (2008). \n\nfn2. R. C. Myers et al.\, _Phys. Rev. Lett._ *95*
 \, 017204 (2005)\; M. Poggio et al.\, _Phys. Rev. B_ *72*\, 235313 (2005)\
 ; N. P. Stern et al.\, _Phys. Rev. B_ *75*\, 045329 (2007). \n\nfn3. W. Pa
 cuski et al.\, _Phys. Rev. B_ *73*\, 035214 (2006)\; ibid. *76*\, 165304 (
 2007)\; _Phys. Rev. Lett._ *100*\, 037204 (2008).\n\nfn4. J. Szczytko et a
 l.\, Solid State Commun. 99\, 927 (1996).\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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