A -type antiferromagnetic order in the Zintl-phase insulator EuZn2 P2

Zintl phases, containing strongly covalently bonded frameworks with separate ionically bonded ions, have emerged as a critical materials family in which to couple magnetism and strong spin-orbit coupling to drive diverse topological phases of matter. Here we report the single-crystal synthesis, magnetic, thermodynamic, transport, and theoretical properties of the Zintl compound EuZn2P2 that crystallizes in the anti-La2O3 (CaAl2Si2) P-3m1 structure, containing triangular layers of Eu2+ ions. In-plane resistivity measurements reveal insulating behavior with an estimated activation energy of Eg=0.11eV. Specific heat and magnetization measurements indicate antiferromagnetic ordering at TN=23K. Curie-Weiss analysis of in-plane and out of plane magnetic susceptibility from T=150 to 300 K yields peff=8.61 for μ0H⊥c and peff=7.74 for μ0H//c, close to the expected values for the 4f7 J=S=7/2 Eu2+ ion and indicative of weak anisotropy. Below TN, a significant anisotropy of χ⊥/χ//≈2.3 develops, consistent with A-type magnetic order as observed in isostructural analogs and as predicted by the density functional theory calculations reported herein. The positive Weiss temperatures of θW=19.2K for μ0H⊥c and θW=41.9K for μ0H//c show a similar anisotropy and suggest competing ferromagnetic and antiferromagnetic interactions. Comparing Eu magnetic ordering temperatures across trigonal EuM2X2 (M= divalent metal, X= pnictide) shows that EuZn2P2 exhibits the highest ordering temperature, with variations in TN correlating with changes in expected dipolar interaction strengths within and between layers and independent of the magnitude of electrical conductivity. These results provide experimental validation of the crystochemical intuition that the cation Eu2+ layers and the anionic (M2X2)2- framework can be treated as electronically distinct subunits, enabling further predictive materials design.