Electrically insulating properties of the 5d double perovskite Sr_2YOsO_6

摘要

A high-pressure-synthesized double perovskite Sr_2YOsO_6 was investigated by synchrotron X-ray diffraction and measurements of its magnetic susceptibility, specific heat capacity, complex impedance, and complex dielectric constant. It crystallized into a monoclinic double perovskite structure (P2_1) with complete ordering of the Y and Os atoms. Its magnetic behaviors, including the antiferromagnetic transition temperature (∼52 K), Curie-Weiss effective moment [3.48(5) μ_B/Os], and Weiss temperature [-350.1(7) K], were close to the respective values of Sr_2YOsO_6 previously synthesized without an applied pressure of 6 GPa. Transport property measurements revealed that the lower limit of the activation energy was 192(1) meV and the charge gap remained open regardless of the presence of magnetic order, conflicting with the electron delocalization predicted by theoretical calculations. Further consideration, including theoretical and experimental investigations of the roles of spin-orbit coupling and U of the 5d electrons of Os 5d-t_(2g) ~3, may assist in understanding the general magnetic and insulating behaviors of quasi-half-filled 5d-t_(2g) ~3oxides in the perovskite category toward the use of 5d double perovskite for magnetic applications.