Regensburg 2002 – wissenschaftliches Programm

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MA: Magnetismus

MA 5: Spindynamik / Ummagnetisierungsvorgänge

MA 5.6: Vortrag

Montag, 11. März 2002, 17:45–18:00, H10

Optical second harmonic generation and femtosecond spin dynamics in antiferromagnetic NiO — •Wolfgang Hübner, Oleksandr Ney, Khompat Satitkovitchai, and Ricardo Gómez-Abal — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany

Optical second harmonic generation (SHG) is very sensitive to antiferromagnetism, in particular also at interfaces of cubic materials such as NiO (001), since it couples linearly to the antiferromagnetic order parameter. To theoretically address the SHG response of the bulk and (001) surface of NiO we compute the electronic structure in two alternative ways: (a) from a parametrized theory that combines a multi-band Hubbard model with crystal field theory (b) using ab initio quantum chemistry for NiO₅⁸⁻ and NiO₆¹⁰⁻ clusters. Spin-orbit coupling is added perturbatively. SHG computed in this way reveals strong magnetic response from the d-d intragap transitions in NiO, which are inaccessible by conventional linear magneto-optics. This antiferromagnetic response is further exploited for spin dynamics and exhibits three effects if dynamically addressed: (a) ultrafast bleaching, (b) femtosecond periodic de- and rephasing, (c) long-lived magnetic coherence. By the inclusion of the laser field pulse shaping is used to attempt at sub-picosecond magnetic switching in NiO.