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.

Automated summary

By embedding ultra-small ZrO2 nanopillars, the strain distribution of La2/3Sr1/3MnO3 films was controlled, leading to rational manipulation of their functional properties. Increasing the number of nanopillars resulted in a significant decrease in the Curie temperature and metal-insulator transition temperature of the films, demonstrating the remarkable tuning capability of vertical tensile stress.