The Role of B‑Site\nDistribution in Ca<sub>2</sub>FeReO<sub>6</sub>

This study systematically investigates the spin glass\nbehavior\nof the double perovskite Ca<sub>2</sub>FeReO<sub>6</sub>. Building\non previous research, we developed a formula to quantify the distribution\nof ions at the B-site, incorporating next-nearest-neighbor interactions.\nUsing molecular field theory and Monte Carlo simulations, we examined\nthe influence of different arrangements of B-site ions on frustration\neffects. The B-site is divided into <i>a</i>-site and <i>b</i>-site, with the number of nearest neighbors from Fe<sup><i>a</i></sup> to Fe<sup><i>b</i></sup> (and\nvice versa) defined as <i>Z</i><sub><i>x</i></sub> (<i>Z</i><sub><i>y</i></sub>). The strongest\nfrustration occurs when <i>Z</i><sub><i>x</i></sub> (or <i>Z</i><sub><i>y</i></sub>) ≈ 2\nand <i>Z</i><sub><i>y</i></sub> (or <i>Z</i><sub><i>x</i></sub>) ≈ 5, resulting in a radial\npattern under comparable conditions. Significant frustration effects\nare also observed when <i>Z</i><sub><i>x</i></sub> (or <i>Z</i><sub><i>y</i></sub>) ≈ 3\nand <i>Z</i><sub><i>y</i></sub> (or <i>Z</i><sub><i>x</i></sub>) ≈ 4. These effects are reflected\nin the variations in ground-state magnetization and the thermal energy\nstep in relation to <i>Z</i><sub><i>x</i></sub> and <i>Z</i><sub><i>y</i></sub>. The model proposed\nin this study is applicable to most B-site disordered perovskite systems\nas well as other chemically disordered frustrated systems.