Exchange interactions in Y3Fe5-xCrxO12 fabricated by a sol-gel method

The Cr-containing YIG we examined, and the exchange interactions and site distributions were studied by ⁵⁷Fe Mossbauer spectroscopy. The exchange parameters for Y₃Fe_4.5Cr_0.5O₁₂ were J_ad=-52.23 k_B, J_aa=-27.85 k_B and J_dd=-39.16 k_B, and their values become larger as the amount of Cr decreases in garnet. The results show that chromium in Y₃Fe_5-xCr_xO₁₂ compounds (x=0.0, 0.25, 0.5, and 1.0) occupy octahedral sites. The lowering of magnetic ordering temperature results from replacing Fe³⁺ by Cr³⁺ in the octahedral sites. Mossbauer spectra can be analyses using 3 or 4 sets of six Lorentzians with increasing amount of Cr³⁺. It results from the distribution (₄C_n ) of Fe³⁺ and Cr³⁺ at octahedral sites. The ratios of areas, a, d₁, d₂, d₃, in Y ₃Fe_4.5Cr_0.5O₁₂ are 0.33, 0.22, 0.28, 0.14, respectively