Anomalous Nernst effect and thermal conductivity in Co3Sn2S2 polycrystals

Abstract

A polycrystalline sample of Co3Sn2S2 shandite was synthesized using spark plasma sintering for its densification. The unit cell parameters, a = 5.3688(1) Å and c = 13.1797(1) Å, refined from room temperature X-ray diffraction data, confirm the R-3m shandite structure. The frustrated nature of the Co magnetic network is invoked to explain the low effective paramagnetic moment of Co, μeff = 1.04μB/Co, whereas the ferromagnetic Curie temperature, TC = 175K, determined from T-dependent magnetic susceptibility corresponds to the metal to metal transition at that temperature. Interestingly, the residual resistivity ratio and resistivity values indicate that the electronic transport is driven by the in-plane contribution. This behaviour close to that of ab-plane transport of Co3Sn2S2 crystal fits well with the measurement of an anomalous Nernst effect (ANE). The latter reaches at T = 100K a maximum value Sxy = +1.5 μV K−1, i.e. a reduction by a factor of ≈2 as compared to crystal, explained by the reduction for the magnetization, M, of the former. This is also demonstrated by the H-dependent Sxy and M loops that match very well. Similarly, a hysteresis is found for the thermal conductivity demonstrating the existence of an anomalous thermal Hall effect of about 5 % of the total thermal conductivity. This study shows that ANE can be also measured in ceramics of Weyl ferromagnets.