Analysis of the Difference between the Pyroxenes LiFeSi2O6 and LiFeGe2O6 in Their Spin Order, Spin Orientation, and Ferrotoroidal Order

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• 作者：Changhoon Lee ; Jinhee Kang ; Jisook Hong ; Ji Hoon Shim ; Myung-Hwan Whangbo
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：February 25, 2014
• 年：2014
• 卷：26
• 期：4
• 页码：1745-1750
• 全文大小：279K
• 年卷期：v.26,no.4(February 25, 2014)
• ISSN：1520-5002

文摘

The pyroxenes LiFeSi₂O₆ and LiFeGe₂O₆ are isostructural and isoelectronic, but they differ in their spin order, spin orientation and ferrotoroidal order. The reasons for these differences were probed by density functional theory electronic structure calculations and magnetic dipole鈥揹ipole (MDD) interaction energy calculations. The ferromagnetic Fe-zigzag chains of LiFeSi₂O₆ arise from the antiferromagnetic interchain spin exchanges and the antiferromagnetic Fe-zigzag chains of LiFeGe₂O₆ from the antiferromagnetic intrachain spin exchange. The preferred spin orientations of LiFeGe₂O₆ and LiFeSi₂O₆ are not caused by spin鈥搊rbit coupling but by MDD interactions. LiFeSi₂O₆ undergoes a ferrotoroidal order because it has spin exchange rings made up of an even number of antiferromagnetic spin exchanges paths with comparable strengths. A ferrotoroidal order is not expected for LiFeGe₂O₆ because it has no such spin exchange rings.