Unusual magnetic and charge transport properties in In-Substituted Half-Metallic Kagome Ferromagnet Co3Sn2S2

Abstract: The kagome ferromagnet Co3Sn2S2 has been studied extensively for its unusual topology of electronic bands, origin of ferromagnetism and strong coupling between magnetism and charge transport. To understand the role of nonmagnetic element Sn, we have investigated magnetic, transport, and electronic structure of the isostructural compound Co3SnInS2, where all the Sn (divalent) atoms in the Co3Sn Kagome layer are replaced by In (trivalent) atoms. We find long-range ferromagnetic order is nearly quenched in Co3SnInS2. The system exhibits predominantly antiferromagnetic correlations with only a very small net magnetic moment and turns ferromagnetic in the presence of an external magnetic field. Transport measurements show a semiconducting behaviour at low temperatures. Magnetoresistance shows a nonmonotonic field dependence, changing from negative to positive with increasing magnetic field. An anomalous Hall effect is observed, but its magnitude is significantly reduced compared to Co3Sn2S2 where the topological character of the Fermi surface plays a dominant role. These results indicate that substitution of Sn by In in the Co3Sn plane not only suppresses the topological electronic features of the transport electrons but drives the system away from the ferromagnetic Half-metallicity to an almost nonmagnetic semiconducting state with unusual paramagnetic response. Electronic structure calculations are consistent with some of these observations.