Asymmetry of second harmonic generation in magnetic thin films under circular optical excitation

We show that right- and left-handed circularly polarized optical excitation can lead to a different intensity of the second harmonic generation in mag netic thin films. This kind of asymmetry arises due to an interference of n onlinear optical waves of crystallographic and/or magnetic origin. In contr ast to linear optics, the equivalence between the magnetization reversal an d the change of the light helicity can be broken. These conclusions are con firmed by experimental studies of the nonlinear asymmetry in thin films of magnetic garnets.