Superconductivity and ferromagnetism are very rarely found to co-exist in natural materials. However, artificially fabricated nanostructures can now be produced where a superconductor, YBa2Cu3O7-x (YBCO) and colossal magneto-resistance magnetic material, La2/3Ca1/3MnO3 (LCMO) are grown in alternating layers on a SrTiO3 substrate. These structures exhibit novel quantum states that do not exist in the constituent materials, and such systems are of potential interest for spintronics applications. Off-specular neutron reflectivity measurements performed on CRISP have revealed rich in-plane magnetisation behaviour. On cooling through the cubic to tetragonal phase transition of the SrTiO3 subphase, the Bragg peak resulting from the multilayer structure splits due to the twinning of the SrTiO3 crystal. On cooling further, through the superconducting transition temperature of the film, the Bragg feature splits again as shown in the figure. This is indicative of the formation of a stripe domain structure with a length scale of tens of microns. This large length scale gives clues as to the mechanism driving the interaction between superconductivity and magnetism in these films, providing a tantalising glimpse into the interplay between these two effects in the multilayer structure.
J Chakhalian, J Strempfer, G Khaliullin, C Bernhard, G Cristiani, H-U Habermeier, B Keimer (Max Planck Institute, Germany), T Charlton and R Dalgliesh (ISIS), JW Freeland and G Srajer (Argonne National Lab, USA), J Cezar (ESRF, France)
Research date: December 2006
J Chakhalian et al., Nature Physics 2 (2006) 244.