Magnetic second harmonic generation in centrosymmetric CoO, NiO, and KNiF3

Optical second harmonic (SH) spectroscopy in the centrosymmetric antiferromagnets CoO, NiO, and KNiF3 reveals pronounced signals below the Neel temperature which couple quadratically to the magnetic order parameter. The SH process roots in resonance enhanced magnetic-dipole and electric-dipole excitations between the 3d levels of the transition-metal ions in the crystal field. Different magnetic structures and differently oriented T and S domains are distinguished with a high degree of discrimination, thus demonstrating the feasibility of nonlinear optical techniques for a spatially resolved investigation of antiferromagnetic crystals and thin films. (C) 2003 American Institute of Physics.