Sb-doped kagome antiferromagnet FeGe: Superlattice structure and spin-reorientation transition

Abstract

Kagome lattice, a two-dimensional corner-sharing triangle network, can be realized in a real material and thus host many interesting physical phenomena. Charge density wave, anomalous Hall effect and antiferromagnetism have been discovered in a typical kagome material FeGe. Here, we report the effects of Sb doping on its crystal structure, magnetic and electrical transport properties. Charge density wave is suppressed completely by only a doping level of x = 0.05 in FeGe_1-xSb_x. A $\sqrt{3}\times \sqrt{3}\times 2$ superlattice is realized at room temperature when the doping level of Sb reaches x = 0.12. The structure distortion of the supercell for the Fe kagome and Ge honeycomb planes are unveiled from single crystal x-ray diffraction measurements. Sb doping can only suppress the A-type antiferromagnetism mildly in FeGe, and induce a spin-reorientation transition when the doping level x is 0.1 or larger. The spin-reorientation transition can be modulated by the doping level as well as the external magnetic field in FeGe_1-xSb_x. No detectable transport or thermodynamic signals can be identified for the spin-reorientation transition, indicating a subtle change in the electronic structure or magnetic entropy.