Cristobalite-Related Phases in the KAlO2–KAlSiO4 System

Magnetic properties of ordered perovskites Ba2LnIrO6 (Ln=Sm, Eu, Gd, and Yb) are reported. Their magnetic susceptibilities were measured from 2 to 350 K. The 151Eu M?ssbauer spectrum of Ba2EuIrO6 and the electronic paramagnetic resonance (EPR) spectrum of Ba2GdIrO6 were measured at room temperature. Ba2EuIrO6 and Ba2SmIrO6 show Van Vleck paramagnetism. A spin–orbit coupling constant of the Eu3+ ion is determined to be 364 cm-1. The M?ssbauer spectrum of Ba2EuIrO6 shows that the Eu ion is in the trivalent state, and the symmetry of the Eu site is slightly distorted from an octahedral symmetry because of the existence of a quadrupole interaction. The magnetic susceptibilities of Ba2GdIrO6 and Ba2YbIrO6 follow the Curie law and the crystal field splitting of the Yb3+ ion is calculated. The g value of the Gd3+ ion in Ba2GdIrO6 is determined to be 1.99 and Gd3+ is very slightly affected by the crystal field from the EPR measurement.