Direct Observation of Fe-Ge Ordering in Fe5-xGeTe2 Crystals and Resultant Helimagnetism
- Direct Observation of Fe-Ge Ordering in Fe5-xGeTe2 Crystals and Resultant Helimagnetism
- 박태언; 김광수; Trinh Thi Ly; Jungmin Park; Kyoo Kim; Hyo-Bin Ahn; Nyun Jong Lee; Ganbat Duvjir; Nguyen Huu Lam; Kyuha Jang; Chun-Yeol You; Younghun Jo; Se Kwon Kim; Changgu Lee; Sanghoon Kim; Jungdae Kim
- Issue Date
- Advanced functional materials
- VOL 온라인게재, 2009758
- Microscopic structures and magnetic properties are investigated for Fe5？xGeTe2 single crystal, recently discovered as a promising van der Waals (vdW) ferromagnet. An Fe atom (Fe(1)) located in the outermost Fe5Ge sublayer has two possible splitsites which are either above or below the Ge atom. Scanning tunneling microscopy shows √3 × √3 superstructures which are attributed to the ordering of Fe(1) layer. The √3 × √3 superstructures have two different phases due to the symmetry of Fe(1) ordering. Intriguingly, the observed √3 × √3 ordering breaks the inversion symmetry of crystal, resulting in substantial antisymmetric exchange interaction. The temperature dependence of magnetization reveals a sharp magnetic anomaly suggesting helical magnetism of the Fe5？xGeTe2 due to its noncentrosymmetricity. Analytical study also supports that the observed ordering can give rise to the helimagnetism. The work will provide essential information to understand the complex magnetic properties and the origin of the new vdW ferromagnet, Fe5？xGeTe2 for future topologybased spin devices.
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