Ferroelectricity Induced by Oxygen Isotope Exchange in Strontium Titanate Perovskite

Ferroelectricity was induced in $\mathrm{SrTiO}{}_3$ by the isotope exchange of ${}^{18}\mathrm{O}$ for ${}^{16}\mathrm{O}$. Dielectric measurements confirmed the ferroelectricity of $\mathrm{SrTi}{}^{18}\mathrm{O}{}_3$, showing a peak at 23 K. A hysteresis loop in the $D$ vs $E$ measurement and TO phonon observed in the Raman spectra supported the evolution of ferroelectricity in $\mathrm{SrTi}{}^{18}\mathrm{O}{}_3$. This is the first demonstration of $\mathrm{SrTi}\mathrm{O}{}_3$ becoming ferroelectric without the application of external fields or the introduction of a random field through cation substitution.