Ultrafast magnetic switching and nonlinear optics in NiO the need to go beyond the electric dipole approximation.

Georgios Lefkidis

Technische Universität Kaiserslautern

The discrete energy levels of the antiferromagnetic materials can be explicitly addressed by a laser pulse, and induce a population redistribution. In combination with SOC this repopulation can lead to switching of the magnetic state of a magnetic material.
The intragap energy levels of the NiO(001) surface are obtained with two different quantum chemistry methods. The first one consists of the single excitation configuration-interaction (CIS) technique followed by a ligand field theory model. The second is the multiconfigurational complete active space (MC-SCF) method, with which each intragap d level is calculated and optimized separately.
The second order susceptibility tensor is calculated within the electric dipole approximation. The effects of spin-orbit coupling are studied, and a detailed analysis of the effects of the inclusion of nonlocalities from magnetic dipoles and electric quadrupoles is performed. Finally the effect of phonons within the frozen phonon approximation is discussed.