Phase transitions in ilvaite, a mixed-valence iron silicate I. A57Fe Mössbauer study of magnetic order and spin frustration

✍ Scribed by Kan Xuemin; Subrata Ghose; B. D. Dunlap

• Publisher: Springer-Verlag
• Year: 1988
• Tongue: English
• Weight: 556 KB
• Volume: 16
• Category: Article
• ISSN: 0342-1791
• DOI: 10.1007/bf00201330

✦ Synopsis

llvaite, Ca (Fe 2 +,Fe 3 +)Fez + Si208(OH) shows two magnetic phase transitions, which have been studied by M6ssbauer spectroscopy within the temperature range 120-4 K. The continued charge localization between Fe 2+ and Fe 3 + ions in octahedral A-sites causes the Fe 2 + -Fe 3 + interaction to be ferromagnetic, although the overall magnetic order is antiferromagnetic. The thermal evolution of the hyperfine fields at the Fe 2 § (A) and Fe 3 + (A) sites indicates Bhf: 328 and 523 kOe respectively at 0 K and TN1 = 116K. The corresponding values for Fe z + (B) site are: Bhf 186 kOe and TN2 = 36K. An additional hyperfine field exists at the Fe 2+ (B) site within the temperature range 116-36K due to short-range order induced by the spin ordering in A sites. The considerable difference between the two magnetic transition temperatures is due to spin frustration, because the Fe z + (B) site occurs on a corner common between two triangles with respect to two sets of Fe z+ (A) and Fe 3 + (A) sites with opposite spin directions.