Absence of a polar phase in perovskite chromite RCrO₃ (R=La and Pr)

Magnetic and dielectric properties have been studied for LaCrO₃, PrCrO₃, and their solid solution La_0.5Pr_0.5CrO₃, which belong to a family of the ferroelectric orthochromite series RCrO₃ (R: rare earths). The magnetic measurements confirm that the materials show canted antiferromagnetic ordering at 240–288 K. Neutron diffraction patterns could be fitted with the centrosymmetric Pnma, which is different from the non-centrosymmetric structure proposed for the ferroelectric phase of NdCrO₃. The large dielectric constants are likely due to the hopping of charge carriers as proposed previously for other chromites.