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 Fe^a to Fe^b (and vice versa) defined as Z_x (Z_y). The strongest frustration occurs when Z_x (or Z_y) ≈ 2 and Z_y (or Z_x) ≈ 5, resulting in a radial pattern under comparable conditions. Significant frustration effects are also observed when Z_x (or Z_y) ≈ 3 and Z_y (or Z_x) ≈ 4. These effects are reflected in the variations in ground-state magnetization and the thermal energy step in relation to Z_x and Z_y. The model proposed in this study is applicable to most B-site disordered perovskite systems as well as other chemically disordered frustrated systems.