Vertical Strain Engineering of Epitaxial La2/3Sr1/3MnO3 Thin Films by Spontaneously Embedding ZrO2 Nanopillar Arrays

Rational control of local strain distributions and thus the functional properties of epitaxial thin films has been a long-standing goal in the development of new physics and novel devices based on strain-sensitive materials. Here, the fabrication of La2/3Sr1/3MnO3 (LSMO) films with strain fields arising from vertical epitaxial embedding of ultra-small ZrO2 nanopillars, diameter 4.0 +/- 0.6 nm, is reported. High quality films are obtained with average distance between adjacent nanopillars of 9.0 +/- 0.3 nm for x = 0.2 in (LSMO)(1-)(x):(ZrO2)(x). The strain distribution of the vertical interface is analyzed in detail and the dominant state of the interfacial strain is verified. Remarkably, with increasing x, the Curie temperature T-C and metal-insulator (MI) transition temperature T-MI show a surprisingly large depression, revealing the significant tuning capability of the vertical tensile stress originating from the small-size ZrO2 pillars. A systematic tunability of the low field magnetoresistance is also found. The field dependence of the magnetization exhibits both horizontal and vertical shifts. The exchange bias field H-E increases with increasing x, while magnetization shift M-shift is unchanged. The results suggest the possibility of strain tuning through epitaxial nanostructures for multifunctional applications across many fields with appropriate selection of matrix and nanopillar materials.