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Second harmonic generation in the centrosymmetric antiferromagnet NiO
M Fiebig1, D Fröhlich, T Lottermoser
1Institut für Physik, Universität Dortmund, 44221 Dortmund, Germany.
Physical Review Letters
|October 3, 2001
Summary
Second harmonic generation (SHG) was observed in NiO below its Néel temperature, despite inversion symmetry. This phenomenon arises from combined magnetic and electric dipole transitions, enabling domain investigation.
Area of Science:
- Solid State Physics
- Materials Science
- Nonlinear Optics
Background:
- Nickel oxide (NiO) possesses crystalline and magnetic lattice inversion symmetry.
- Second Harmonic Generation (SHG) is a nonlinear optical process typically forbidden in centrosymmetric materials.
Purpose of the Study:
- To investigate the origin of observed Second Harmonic Generation (SHG) in NiO below its Néel temperature.
- To explore the potential of SHG for probing magnetic domains in NiO.
Main Methods:
- Spectroscopic analysis of NiO below the Néel temperature.
- Investigation of nonlinear optical properties, specifically SHG.
- Analysis of the coupling between nonlinear polarization and the magnetic order parameter.
Main Results:
- SHG was observed in NiO despite its inversion symmetry, below the Néel temperature.
- The SHG signal originates from resonant, combined magnetic-dipole and electric-dipole transitions between Ni(2+) (3d)(8) levels.
- A quadratic coupling between nonlinear polarization and the magnetic order parameter was identified.
Conclusions:
- The observed SHG in NiO is attributed to specific electronic transitions enhanced by resonance.
- The quadratic coupling allows for the investigation of individual magnetic domains in NiO using SHG.
- SHG provides a sensitive probe for studying magnetic structures and phase transitions in materials like NiO.