Splitting of the ultraviolet plasmon resonance from controlling FePt nanoparticles morphology

We show a designed FePt nanoparticles for embedding in a single crystal MgO matrix and demonstrate plasmon resonance absorption can appear in the ultraviolet region. The state of the FePt alloy is confirmed by X-ray photoelectron spectroscopy and selected area electron diffraction. By increasing the laser energy density from 4 to 6 J/cm2, the shape of the FePt nanoparticles is changed from quasi-spherical to quasi-elliptical. Compared with pure MgO, a single plasmon resonance peak at 234 nm was found in the ultraviolet region for the embedded FePt. Increasing the laser energy density induces peak splitting into two peaks, located at 225 and 262 nm, respectively. With a high laser energy density, a red-shift and a blue-shift are observed for the two peaks, respectively. These results are accordance with the theoretical calculations. The ultraviolet plasmon resonance absorption for FePt NPs can be tuned by changing the shape of the nanoparticles.