Evidence for surface spin structures from first order reversal curves in magnetic topological semimetal

Abstract

We study magnetization reversal and first order reversal curves for two different magnetic topological semimetals, Co3Sn2S2 and Fe3GeTe2, in a wide temperature range between 80 K and 180 K. For the magnetization hysteresis loops, we observe strong temperature dependence of the initial (low-temperature) step-like magnetization switchings, so asymmetric regions of slanted magnetization appears above 140 K. Usually, similar behavior is ascribed to appearance of the second, temperature-induced magnetic phase. However, first order reversal curve analysis shows two-phase behavior even at lowest temperatures of our experiment. While the bulk ferromagnetic phase is of high temperature dependence, the second magnetic phase demonstrates perfect temperature stability below the Curie temperature. We connect the robust second phase with the surface spin textures, which are inherent for magnetic topological semimetals, so the excellent temperature stability is due to the topological protection of the semimetal surface states. This conclusion is also supported by the characteristic bow-tie magnetic hysteresis loops.

Second-Harmonic Response in Magnetic Nodal-Line Semimetal Fe3GeTe2

“…[21,22] By Bitter decoration technique, [69,70] we also confirmed the labyrinth domain structure [23,24] for our FGT samples, as well as the hexagonally packed skyrmions. [22] Also, the characteristic bowtie magnetic hysteresis loops are shown for our FGT samples, [71] which are usually ascribed to the skyrmions. Deformation of the skyrmion lattice can be responsible for the observed hysteresis with the magnetic field sweep direction.…”