Europium monoxide is both an insulator and a Heisenberg ferromagnet (Tc=69 K).
In the present thesis, the author has investigated the electronic structure of different
types of EuO by density functional theory. The on-site Coulomb interaction of the
localized Eu 4f and 5d electrons, which is wrongly treated in the standard generalized
gradient approximation method, is found to be crucial to obtain the correct insulating
ground state as observed in experiments. Our results show that the ferromagnetism
is stable under pressure, both hydrostatic and uniaxial. For both types of pressure
an insulator-metal transition is demonstrated. Moreover, the experimentally observed
insulator-metal transition in oxygen deficient and gadolinium-doped EuO is reproduced
in our calculations for impurity concentrations of 6.25% and 25%. Furthermore, a 10-
layer EuO thin film is theoretically predicted to be an insulator with a narrow band gap
of around 0.08 eV, while the Si/EuO interface shows metallic properties with the Si and
O 2p as well as Eu 5d bands crossing the Fermi level.
|Date of Award||May 2011|
- Physical Science and Engineering
|Supervisor||Udo Schwingenschloegl (Supervisor)|