Unique structure type and antiferromagnetic ordering in semiconducting Eu2InSnP3

The multitude of bonding motifs that can arise from the main group elements in pnictides leads to ternary compounds with rare earths that span insulating and metallic behavior, layered and channeled compounds, and ferrimagnetic and antiferromagnetic ordering. Here we present the quaternary pnictide Eu2InSnP3, which forms in the orthorhombic space group Pnma. The Eu2+ ions in Eu2InSnP3 form a hollandite-like channeled matrix of edge-sharing EuP6 octahedra, while the interior of the channels are filled with ethane-like InSnP6 units. Despite the challenges in differentiating In and Sn by X-ray diffraction, their equimolar concentration and ordering in this compound is enforced by the need for charge balance, which leads to semiconducting behavior. First-principles simulations confirm the stability of the experimentally found crystal structure and show that the smallest gap to be indirect of about 0.5 eV, but close in energy to a direct gap. The magnetic behavior of Eu2InSnP3 is complex, with a low-field antiferromagnetic ordering at TN = 12 K and a spin-flop transition around 0.8 T at 2 K. The progression of magnetic states is complex, driven by the two inequivalent Eu sites in the compound and the low anisotropy of the 4f7 Eu ion.