Exchange coupling and exchange bias inLa0.7Sr0.3MnO3–SrRuO3 superlattices

Abstract

La0.7Sr0.3MnO3–SrRuO3 superlattices with and without nanometrically thinSrTiO3,BaTiO3 andBa0.7Sr0.3TiO3 interlayerswere grown by pulsed laser deposition. Transmission electron microscopy studies showed coherent growthof La0.7Sr0.3MnO3, SrRuO3 and SrTiO3 layers with atomically sharp interfaces, even if individual layers wereas thin as one or two unit cells. In contrast, misfit dislocations andunit cell high interfacial steps were observed at the interfaces betweenBaTiO3 and one of the ferromagnetic layers. The presence of the interlayers as well as theseextended defects had a significant influence on the magnetic properties of the superlattices,especially on the antiferromagnetic interlayer exchange coupling between theLa0.7Sr0.3MnO3 andSrRuO3 layers and the exchange biasing. Surprisingly, exchange biasing was found to increase withdecreasing strength of the antiferromagnetic interlayer exchange coupling. This wasexplained by different magnetization reversal mechanisms acting in the regimes of strongand weak interlayer exchange coupling.