A Peculiar Topological Hall Effect in Noncentrosymmetric Ternary Carbide GdCoC2

A peculiar topological Hall effect (THE) is reported in a noncentrosymmetric ternary carbide GdCoC2. The GdCoC2 reveals a magnetic ordering transition from paramagnetic to ferromagnetic state at the Curie temperature T-C = 15.6 K, followed by a commensurateincommensurate phase transition at T-t = 14.1 K. Below T-t, the competition between an external magnetic field and magnetic interactions, including the Dzyaloshinskii-Moriya interaction, would give rise to characteristic spin textures with non-zero scalar spin chirality chi(ijk), or even topologically protected spin configurations like skyrmions, for which the exotic spin-charge coupled phenomena are induced. Besides a large negative magnetoresistance (MR) up to similar to-52% at 14 K, a remarkably sharp topological Hall signal is observed with almost no anomalous Hall resistivity below 10 K. The topological Hall resistivity (rho(T)(xy)) of GdCoC2 reaches a maximum value of similar to 0.23 mu Omega cm at 3 K under mu H-0 = 0.6 T. The mechanism underlying the exceptional THE with relatively large rho(T)(xy) value in GdCoC2 is discussed in detail.