Evidence of spin reorientation and anharmonicity in kagome ferromagnet Fe₃Sn₂

Recently discovered massive Dirac fermions and room temperature skyrmions in the ferromagnetic kagome metal Fe3Sn2 have attracted extensive attention due to the potential applications in topological and spintronic devices. Because of its centrosymmetric lattice, the topological spin texture in Fe3Sn2 arises primarily from the competition between anisotropy and exchange interaction. In this Letter, we have identified the spin-reorientation at around 80 K by the magnetization and AC-susceptibility measurements. The evolution of the anisotropy is revealed by neutron powder diffraction data from 18 to 700 K, where the "breathing"-like kagome structure evolves into an ideal kagome lattice at higher temperature. Meanwhile, the deviation between the experimental and calculated results on heat capacity at high temperature and the softening of optical phonon modes in Raman spectra suggest the presence of anharmonic phonons in Fe3Sn2, which is responsible for the degeneracy of lattice thermal conductivity at high temperature. Our study indicates that Fe3Sn2 possesses a promising future in the design and development of topological, spintronic as well as thermoelectric devices.