Two-Dimensional Ultrathin FeSn Kagome Metal with Defect-Dependent Magnetic Property.

Two-dimensional (2D) FeSn, which is a room-temperature ferromagnetic kagome metal, has potential applications in spintronic devices. However, the systematic synthesis and magnetic study of 2D FeSn single crystals have rarely been reported. Here we have synthesized 2D hexagonal and triangular FeSn nanosheets by controlling the amount of FeCl precursors in the chemical vapor deposition (CVD) method. It is found that the hexagonal FeSn nanosheets exist with Fe vacancy defects and show no obvious coercivity. While the triangular FeSn nanosheet has obvious hysteresis loops at room temperature, its coercivity first increases and then remains stable with an increase in temperature, which should result from the competition of the thermal activation mechanism and spin direction rotation mechanism. A first-principles calculation study shows that the Fe vacancy defects in FeSn can increase the distances between Fe atoms and weaken the ferromagnetism of FeSn. The resulting 2D FeSn nanosheets provide a new choice for spintronic devices.