Comparison of the magnetic properties of Mn₃Fe₂Si₃O₁₂ as a crystalline garnet and as a glass

The crystalline garnet Mn₃Fe₂Si₃O₁₂ and an amorphous phase of the same nominal composition are synthesized at high pressure. The magnetic properties of the two forms are reported. Both phases order antiferromagnetically. The crystalline phase exhibits a Curie-Weiss theta of −37.2 K, with a sharp ordering transition at 12 K. The glassy phase exhibits a larger antiferromagnetic Curie-Weiss theta, of −89.7 K, with a broad ordering transition observed at 2.5 K. The amorphous phase shows a much higher degree of magnetic frustration than the crystalline phase; it exhibits spin-glass behavior and is determined to have an actual composition of Mn₃Fe₂Si₃O₁₃.