Ferroelectric to Quantum Paraelectric Crossover in Mixed Crystals of Isotopic Strontium Titanate

Abstract

Strontium Titanate (SrTiO₃), the most studied and well known quantum paraelectric since sixty years ago, results in a typical ferroelectric when substituting ¹⁶O by ¹⁸O. An effective field approach including quantum considerations of zero point energy explains satisfactorily the behavior of different ferroelectric-quantum paraelectric mixed systems. The isotopic strontium titanate SrTi (¹⁶O_1-x ¹⁸O_x)₃ can then be modelled as a mixed system with a critical composition (x_c = 0.33) at which a crossover between ferroelectric and quantum paraelectric behavior takes place. A discussion is made in terms of dipole interaction strength for both isotopes.

Acknowledgments

We gratefully thank financial support to Spanish MICINN, Grant FIS2008-00715.