The Role of B-Site Distribution in Ca₂FeReO₆

This study systematically investigates the spin glass behavior of the double perovskite Ca2FeReO6. Building on previous research, we developed a formula to quantify the distribution of ions at the B-site, incorporating next-nearest-neighbor interactions. Using molecular field theory and Monte Carlo simulations, we examined the influence of different arrangements of B-site ions on frustration effects. The B-site is divided into a-site and b-site, with the number of nearest neighbors from Fea to Feb (and vice versa) defined as Zx (Zy). The strongest frustration occurs when Zx (or Zy) ≈ 2 and Zy (or Zx) ≈ 5, resulting in a radial pattern under comparable conditions. Significant frustration effects are also observed when Zx (or Zy) ≈ 3 and Zy (or Zx) ≈ 4. These effects are reflected in the variations in ground-state magnetization and the thermal energy step in relation to Zx and Zy. The model proposed in this study is applicable to most B-site disordered perovskite systems as well as other chemically disordered frustrated systems.