Nonlinear optical detection of a ferromagnetic state at the single interface of an antiferromagnetic LaMnO₃/SrMnO₃ double layer

Emergence of a ferromagnetic state at the single interface of two antiferromagnetic perovskite manganites, LaMnO3 and SrMnO3, has been detected with nonlinear magneto-optical Kerr rotation. The samples are composed of approximately four unit cells of each material, with reversed stacking sequence. The existence and orientations of the interface dipole or that of so-called toroidal moment were determined through phase-sensitive second-harmonic detection. Characterization of multiferroic states at the single interfaces, and non-negligible effect of surfaces on the Kerr rotation are demonstrated.