Exchange coupling and exchange bias in La0.7Sr0.3MnO3–SrRuO3 superlattices

La0.7Sr0.3MnO3–SrRuO3 superlattices with and without nanometrically thin SrTiO3, BaTiO3 and Ba0.7Sr0.3TiO3 interlayers were grown by pulsed laser deposition. Transmission electron microscopy studies showed coherent growth of La0.7Sr0.3MnO3, SrRuO3 and SrTiO3 layers with atomically sharp interfaces, even if individual layers were as thin as one or two unit cells. In contrast, misfit dislocations and unit cell high interfacial steps were observed at the interfaces between BaTiO3 and one of the ferromagnetic layers. The presence of the interlayers as well as these extended defects had a significant influence on the magnetic properties of the superlattices, especially on the antiferromagnetic interlayer exchange coupling between the La0.7Sr0.3MnO3 and SrRuO3 layers and the exchange biasing. Surprisingly, exchange biasing was found to increase with decreasing strength of the antiferromagnetic interlayer exchange coupling. This was explained by different magnetization reversal mechanisms acting in the regimes of strong and weak interlayer exchange coupling.