Strain dependence of antiferromagnetic interface coupling in   La0.7Sr0.3MnO3/SrRuO3 superlattices
  We have investigated the magnetic response of La0.7Sr0.3MnO3/SrRuO3 superlattices to biaxial in-plane strain applied in-situ. Superlattices grown on piezoelectric substrates of 0.72PbMg1/3Nb2/3O3-0.28PbTiO3(001) (PMN-PT) show strong antiferromagnetic coupling of the two ferromagnetic components. The coupling field of mu0HAF = 2.8 T is found to decrease by deltaHAF/delta epsilon ~ -520 mT %-1 under reversible biaxial strain mu0HAF at 80 K in a [La0.7Sr0.3MnO3(22)/SrRuO3(55)]15 superlattice. This reveals a significant strain effect on interfacial coupling. The applied in-plane compression enhances the ferromagnetic order in the manganite layers which are under as-grown tensile strain. It is thus difficult to disentangle the contributions from strain-dependent antiferromagnetic Mn-O-Ru interface coupling and Mn-O-Mn ferromagnetic double exchange near the interface, since the enhanced magnetic order of Mn spins leads to a larger net coupling of SrRuO3 layers at the interface. Strain-dependent orbital occupation in a single-ion picture cannot explain the sign of the observed strain dependence, whereas the enhanced Mn order at the interface is qualitatively in line with it. 
Sujit Das, Andreas Herklotz, Eckhard Pippel, Er-Jia Guo, Diana Rata,   Kathrin D\"orr
cond-mat.str-el