Interplay of charge carrier and antiferromagnetic order in metallic triangular lattice GdZn₃P₃

We investigate a hexagonal ScAl₃C₃-type antiferromagnet GdZn₃P₃ single crystal. Compared with antiferromagnetic topological material EuM₂X₂ (M = Zn, Cd; X = P, As), the GdZn₃P₃ features an additional ZnP 3 trigonal planar units. Notably, single-crystal x-ray diffraction analysis reveals that Zn and P atoms within a trigonal planar layer exhibit significant anisotropic displacement parameters with space group P6₃/mmc. Meanwhile, a scanning transmission electron microscopy experiment demonstrates the presence of interstitial P atoms above and below the ZnP honeycomb lattice, suggesting potential ZnP bond instability within the ZnP₃ trigonal layers. Concerning the triangular Gd 3+ layer, the magnetic susceptibility χ (T) and heat capacity measurements reveal an A-type antiferromagnetic order at T_N = 4.5 K. Below T_N, the in-plane χ (T) is nearly 4 times the χ (T) along c axis, indicative of strong magnetic anisotropy for salt-flux-grown GdZn₃P₃ crystal. The density function theory calculation shows that GdZn₃P₃ is an indirect semiconductor with a band gap 0.27 eV, supported by the resistivity measurement on the polycrystal sample. Interestingly, Hall measurements of metallic GdZn₃P₃ crystals grown via salt flux reveal a low concentration of hole carriers, consistent with the previously mentioned presence of interstitial P atoms. Furthermore, these crystals exhibit a pronounced nonlinear anomalous Hall effect below T_N. In contrast, GdZn₃P₃ crystals grown by chemical vapor transport display weak semiconducting behavior. Despite exhibiting a similar T_N, the in-plane χ (T) below T_N in the vapor-transport-grown crystal is approximately half in magnitude compared to that of the salt-flux-grown sample, which supports the hypothesis of charge carrier-mediated Ruderman-Kittel-Kasuya-Yosida interactions. These findings collectively establish GdZn₃P₃ as a compelling model system for investigating the coupling between charge carriers and triangular lattice magnetism within a two-dimensional framework.