Stabilization of antiferromagnetism in 1T-Fe$_{0.05}$TaS$_2$

Abstract

1T-TaS2 is a prototypical charge-density-wave (CDW) system with a Mott insulating ground state. Usually, a Mott insulator is accompanied by an antiferromagnetic state. However, the antiferromagnetic order had never been observed in 1T-TaS2. Here, we report the stabilization of the antiferromagnetic order by the intercalation of a small amount of Fe into the van der Waals gap of 1T-TaS2, i.e. forming 1T-Fe0.05TaS2. Upon cooling from 300 K, the electrical resistivity increases with a decreasing temperature before reaching a maximum value at around 15 K, which is close to the Neel temperature determined from our magnetic susceptibility measurement. The antiferromagnetic state can be fully suppressed when the sample thickness is reduced, indicating that the antiferromagnetic order in Fe0.05TaS2 has a non-negligible three-dimensional character. For the bulk Fe0.05TaS2, a comparison of our high pressure electrical transport data with that of 1T-TaS2 indicates that, at ambient pressure, Fe0.05TaS2 is in the nearly commensurate charge-density-wave (NCCDW) phase near the border of the Mott insulating state. The temperature-pressure phase diagram thus reveals an interesting decoupling of the antiferromagnetism from the Mott insulating state.