Thermal fluctuation of Fe-Ge ordering in Fe5-xGeTe2 single crystals

초록

Fe5-xGeTe2 is a magnetic van der Waals material with a relatively high Curie temperature near room temperature. Fe5-xGeTe2 exhibits unique magnetic properties due to its chemical and structural complexities. In this study, we employed scanning tunneling microscopy (STM) to investigate the thermal fluctuation of Fe-Ge ordering in Fe5-xGeTe2. At low temperatures (79 K), the Fe5-xGeTe2 surface exhibits distinct order with root 3 x root 3 periodicity resulting from the ordered Fe(1) atoms located in the outermost Fe5Ge sublayer, while Fe deficient area shows 1 x 1 hexagonal lattice. At room temperature, on the other hand, structural fluctuations occur as thermal energy drives Fe(1) atom diffusion via a vacancy-mediated process. This results in the temporal rearrangement of the root 3 x root 3 and 1 x 1 regions at their boundaries. These findings provide important insights into the structural and magnetic properties of Fe5-xGeTe2.

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