Magnetic frustration driven nontrivial spin texture in the two-dimensional rare earth electride Tb₂C

Rare-earth carbides (R₂C) provide a cost-effective platform for enhancing magnetic ordering temperatures of rare-earth metals while enabling exotic spin textures [1-4]. We report detailed magnetic characterization of Tb₂C, a layered electride-type compound crystallizing in the trigonal Rm structure. Magnetization measurements reveal a Curie temperature of ~280 K, which is nearly 50 K higher than that of elemental Tb, analogous to the behavior previously observed in Gd₂C [1-3]. The zero-field-cooled and field-cooled magnetization curves exhibit pronounced bifurcation and multiple anomalies between 80 K and 230 K, indicative of magnetic frustration and competing interactions. Step-like metamagnetic transitions are observed in M-H isotherms at 2 K, which vanish for T ≥ 5 K, consistent with field-driven spin reorientation. The effective magnetic moment μ_eff = 9.97 μ_B/Tb³⁺, closely matches the theoretical value for Tb³⁺ (9.72 μ_B), indicating weak crystal-field effects. However, the saturation moment at 2 K is around 10 μ_B/f.u., which is lower than the collinear FM alignment of the Tb³⁺ moments (18 μ_B), suggesting the canting and/or local AFM coupling in the sample. The field-dependent ac susceptibility exhibits strong sensitivity to dc bias, suggesting complex spin dynamics and the potential formation of nontrivial magnetic textures such as skyrmions. These results establish Tb₂C as a promising candidate for studying frustration-induced phenomena and topological spin states in rare-earth-based electride systems.