부산대학교 도서관

Rare-earth orthochromites with distorted perovskite structure (e.g. RCrO3, R = Sm, Gd) have been under strong debate with respect to the origin of their ferroelectric order. Of particular interest is the question of whether such orthochromites are, in fact, magnetically driven improper ferroelectrics, as many rare-earth manganites or orthoferrites. Here we show, by studying at the atomic scale the rare-earth SmCrO3 system that a distortion of the Sm local environment emerges within the paramagnetic phase, near room temperature. Our Electric Field Gradient measurements combined with first-principles calculations show that the emergent phase cannot be simply ascribed to the Pna21 structure as reported for GdCrO3 or SmCrO3. Instead a local inhomogeneous state, where regular non-polar and polar distorted environments coexist, develops at low temperatures. [ABSTRACT FROM AUTHOR]