Anomalous lattice tilting across a magnetic oxide heterostructure

It is well known that the conventional lattice flexibility of an epitaxial layer is restricted by its growth template and bulk counterpart. Here, we report that the interface-engineered (La,Ca)MnO3 layer can exhibit an anomalous lattice-tilting pattern, featured by the interaxis angle alpha that exceeds the range of the lattice flexibility mentioned earlier. By increasing the adjacent CaRuO3 layer thickness, the (La,Ca)MnO3 layer shows a decreasing alpha down to 89.25 degrees, which is out of the flexible range between 93.82 degrees (from the CaRuO3 template) and 89.86 degrees [from the (La,Ca)MnO3 bulk]. The resulting antiparallel lattice tilting makes the (La,Ca)MnO3/CaRuO3 interface similar to a crystal twinning plane to lower the interfacial energy raised by the structural discontinuity. Also, a monotonic reduction of magnetic coercivity (from 205 to 70 Oe) is observed on decreasing alpha (from 90 degrees to 89.25 degrees) in (La,Ca)MnO3 layers, providing an additional approach to tunable magnetic properties without changing the epitaxial strain. Our results not only present a new lattice-engineering strategy of using the interface similar to a crystal-twinning plane in designing heterostructures, but also they reveal the application of such a strategy for tunable magnetic properties beyond the epitaxial strain.