Magnetic Properties of Epitaxially Grown SrRuO3 Nanodots
Using e-beam lithography of epitaxial SrRuO3 films, we succeeded in fabricating nanosized dots of SrRuO3 ranging in size from several hundred nanometers down to 15 nm. Unexpectedly, down to the smallest dot size explored, the samples were found to be magnetic. The Curie temperature depends on the size of the dots, increasing gradually from 149 K in the thin film and dots larger than 500 nm to 157 K at 30 nm dot size. Scanning transmission electron microscopy provides evidence that this behavior results from strain relaxation in the material caused by the removal of lateral constraint around the dot.
This research was done in collaboration with Hongguang Wang, Vesna Srot, and Peter A. van Aken of the StEM group.
Figure1: (a) AFM image of SrRuO3 dot arrays grown on SrTiO3 showing both the 1-unit-cell high substrate surface steps and the dot arrays. The height of the dots is approximately 3 nm. (b) Top view SEM image of a SrRuO3 dot array with a diameter of 20 nm and height of 12 nm.
Figure1: (a) AFM image of SrRuO3 dot arrays grown on SrTiO3 showing both the 1-unit-cell high substrate surface steps and the dot arrays. The height of the dots is approximately 3 nm. (b) Top view SEM image of a SrRuO3 dot array with a diameter of 20 nm and height of 12 nm.
Figure2: (a) Z-contrast STEM image of a cross-sectional cut through a single dot close to its center. (b) Magnified STEM image showing the interface (red arrow) between the dot and the substrate.
Figure2: (a) Z-contrast STEM image of a cross-sectional cut through a single dot close to its center. (b) Magnified STEM image showing the interface (red arrow) between the dot and the substrate.
Figure3: (a) Measured temperature dependence of the magnetization of several samples with different dot sizes in the temperature range close to Tc. All curves are normalized by the magnetization of the film. (b) Curie temperature of the sample plotted as a function of dot diameter.
Figure3: (a) Measured temperature dependence of the magnetization of several samples with different dot sizes in the temperature range close to Tc. All curves are normalized by the magnetization of the film. (b) Curie temperature of the sample plotted as a function of dot diameter.
