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Theses

Etude magnéto-optique de (Ga,Mn)N et (Zn,Cr)Te

Abstract : The field of this thesis is the new diluted magnetic semiconductors (DMS) with the possibility
of a high Curie temperature : (Ga,Mn)N and (Zn,Cr)Te. Previous studies have shown in
both compounds the same valence d4 for the transition metal ions, and ferromagnetic properties
(sometimes paramagnetic for (Ga,Mn)N).
A magneto-spectroscopic study on the internal d-d transition of the Mn at 1.4 eV, performed
on low Mn content GaN epilayers, less than 0.1%, allowed us to develop a crystal eld model
for Mn3+ (3d4) including dynamical Jahn-Teller eect. This hypothesis on d4 conguration of
Mn is also valid for higher Mn doping, up to a few %. Moreover, magnetic circular dichroism at
the band gap energy, in agreement with the magnetization measurements, has shown a standard
DMS with a spin-carrier coupling and a paramagnetic behavior. The measured anisotropy is
weaker than the calculated one from the spectroscopic parameters.
Magnetization, magnetic circular dichroism and Hall eect measurements have shown ferromagnetic
properties with a high disorder. In opposition to standard DMS, the dichroism does
not come from the absorption at the band gap edge but from a deep band. The ferromagnetic
state is not induced by carriers but it is carrier sensitive : a p-type conductivity, obtained with
N codoping, suppresses the ferromagnetism, probably because of a change in the Cr valence.
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Submitted on : Monday, June 26, 2006 - 6:46:51 AM
Last modification on : Tuesday, September 11, 2018 - 11:00:02 AM
Long-term archiving on: : Tuesday, September 18, 2012 - 3:05:11 PM

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Stéphane Marcet. Etude magnéto-optique de (Ga,Mn)N et (Zn,Cr)Te. Physique [physics]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00081752⟩

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