Chemical-induced polar-axis rotation in strained epitaxial Sr1-xBaxMnO3 thin films

Abstract

The development of multiferroic materials with strong magnetoelectric effect has been the object of intensive study in recent years due to their potential applications in data storage technology. The goal is to increase the coupling between magnetic and polar properties, and AMnO3 perovskites (being A = Ca, Sr or Ba) have been proposed as novel candidates with the condition that the unit cell volume is artificially expanded. Two different approaches have been carried out: epitaxial strain engineering in SrMnO3 thin films and Ba doping in bulk SrMnO3. Here we report on the in-plane strain induced polar properties of SrMnO3 thin films probed by optical Second Harmonic Generation (SHG) [4]. Furthermore, the effect of Ba doping in Sr1-xBaxMnO3 films has been studied. Three different Ba-contents have been chosen (x=0.2, 0.3, 0.4). The evolution of the unit cell tetragonality has been analysed using high resolution XRD. With increasing Ba content, the c/a evolution suggests a possible rotation of the polar axis towards the out of plane direction. The correlation between the tetragonality of Sr1-xBaxMnO3 and the polar state of the film will also be shown.