Regensburg 2002 – scientific programme

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O: Oberflächenphysik

O 40: Oxide und Isolatoren (II)

O 40.6: Talk

Friday, March 15, 2002, 12:30–12:45, H45

Parametrized theory for optical second harmonic generation at antiferromagnetic NiO(001) and CoO(001). — •Oleksandr Ney and Wolfgang Hübner — Max-Planck-Institut für Mikrostrukturphysik Weinberg 2, D-06120 Halle, Germany

Surfaces and interfaces of transition-metal oxides play an important role in technological applications. Optical second harmonic generation (SHG) is a nondestructive, easy to implement, powerful tool for the investigation of antiferromagnetic (AF) material properties.

In this work we attempt to compute the SHG response from the (001) surface of Ni⁺⁺ atom in NiO. Calculation of states, active in the optical SHG, is performed using the multiband Hubbard model, Clebsch-Gordan algebra and a parametrized ligand-field approach (suitable for the description of materials with incompletely filled shells of strongly correlated 3d electrons). In this work we assume that exactly two 4s electrons are transferred from the TM atom to the oxygen atom. This gives us the both the ground states Ni..3d⁸4s⁰ in NiO and Co..3d⁷4s⁰ in CoO and excited states Ni..3d⁷4s¹, Ni..3d⁶4s², Co..3d⁶4s¹.

As a result, the static as well as the dynamic behavior of prototypic nonmagnetic and AF nonlinear susceptibility tensor elements are calculated. The SHG spectrum of NiO(001) exhibits AF spectral lines which show ultrafast AF spin dynamics. The dephasing dynamics in this system fulfills two of the basic requirements for data storage devices: (1) high read-write speed, (2) long lasting coherence.