Tailoring magnetic and dielectric properties of Yb2Ti2O7 pyrochlore through structural distortion.

While the unique geometrical frustration of pyrochlore Yb₂Ti₂O₇ has attracted attention, the dielectric and other properties of this pyrochlore beyond frustrated magnetism are not well understood. Here, we report on the fascinating low-temperature dielectric relaxation of Yb_2-xBa_xTi₂O_7-δ (x = 0–0.20) and demonstrate that this phenomenon is related to structural distortion. A-site Ba substitution, which increases the density of point defects and introduces a different atomic radius, enhances the chemical disorder and structural distortion. As a result, the increases in oxygen vacancies and nonmagnetic Ba²⁺ and Yb²⁺ ions dilute the ferromagnetic Yb³⁺–Yb³⁺ interactions, as indicated by the decrease in effective magnetic moment. On the other hand, the distorted octahedra facilitate the hopping of Yb ions, and the random distribution of Ba²⁺ ions at the Yb³⁺ sites gives rise to additional random fields, leading to significantly increased dielectric relaxation. The room-temperature dielectric constant is improved to ∼170, twice that of pristine Yb₂Ti₂O₇. This work provides a comprehensive view of the structural, magnetic, and dielectric properties of Yb₂Ti₂O₇ and lays the foundation for additional research into pyrochlore compounds. [ABSTRACT FROM AUTHOR]