A-type antiferromagnetic order in the Zintl-phase insulator EuZn2P2

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 E-g = 0.11 eV. Specific heat and magnetization measurements indicate antiferromagnetic ordering at T-N = 23 K. Curie-Weiss analysis of in-plane and out of plane magnetic susceptibility from T = 150 to 300 K yields p(eff) = 8.61 for mu H-0 perpendicular to c and p(eff) = 7.74 for mu H-0//c, close to the expected values for the 4 f(7) J = S = 7/2 Eu2+ ion and indicative of weak anisotropy. Below T-N, a significant anisotropy of x(perpendicular to)/x(//) approximate to 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 theta(W) = 19.2 K for mu H-0 perpendicular to c and theta(W) = 41.9 K for mu H-0//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.

Automated summary

This study reports the synthesis and properties of the Zintl compound EuZn2P2 and its electronic structure calculations. The experimental results show that the compound exhibits insulating behavior and undergoes antiferromagnetic ordering at lower temperatures. The magnetic measurements indicate weak anisotropy and competing ferromagnetic and antiferromagnetic interactions. These findings are important for further predictive materials design.