Gadolinium Molybdate, a New Type of Ferroelectric Crystal

Abstract

Ferroelectric properties in gadolinium molybdate are shown to originate from a new mechanism completely different from that in conventional ferroelectric materials. In this crystal the spontaneous polarization results from an elastic instability which gives rise to a spontaneous strain in the original piezoelectric paraelectric phase. The dielectric permittivity of the clamped crystal ($\epsilon _{33}^{}{}_{}{}^x$) is low and independent of temperature, while the elastic constant ($c_{66}^{}{}_{}{}^E$) shows a strong temperature dependence with a marked anomaly at the Curie point.