Disentangling the magneto-optic Kerr effect of manganite epitaxial heterostructures

The magneto-optic Kerr effect can probe the process of magnetization reversal in ferromagnetic thin films and can, thus, be used as an alternative to magnetometry. The Kerr effect is wavelength-dependent and the Kerr rotation can reverse sign, vanishing at particular wavelengths. We investigate the epitaxial heterostructures of ferromagnetic manganite, La0.7Sr0.3Mn0.9Ru0.1O3, by using the polar Kerr effect and magnetometry. The manganite layers are separated by or interfaced with a layer of nickelate, NdNiO3. The Kerr rotation hysteresis loops of trilayers, with two manganite layers of different thicknesses separated by a nickelate layer, have intriguing humplike features when measured with light of 400 nm wavelength. By investigating additional reference samples, we disentangle the contributions of the individual layers to the loops: we show that the humps originate from the opposite sense of the Kerr rotation of the two different ferromagnetic layers, combined with the additive behavior of the Kerr signal. The change of sign of the Kerr rotation for the thinner manganite layer is most likely caused by optical interference.

Automated summary

The magneto-optic Kerr effect can be used to probe magnetization reversal in ferromagnetic thin films and as an alternative to magnetometry. The wavelength-dependent Kerr effect can lead to a reversal in Kerr rotation and disappear at specific wavelengths. Through investigating epitaxial heterostructures, researchers discovered humplike features in the Kerr rotation hysteresis loops of trilayers consisting of ferromagnetic manganite layers separated by a nickelate layer when measured with 400 nm wavelength light. They attribute these features to the opposite Kerr rotation sense of the different ferromagnetic layers and the additive behavior of the Kerr signal. The change in Kerr rotation sign for the thinner manganite layer is most likely caused by optical interference.