Deconvoluting the Magnetic Structure of the Commensurately Modulated Quinary Zintl Phase EuSrZnSnAs.

The structure, magnetic properties, and Eu and Sn Mössbauer spectra of the solid-solution EuSrZnSnAs are presented. A new commensurately modulated structure is described for EuZnSnAs (3 space group, average structure) that closely resembles the original structural description in the monoclinic 2/ space group with layers of Eu, puckered hexagonal ZnAs sheets, and ZnAs ethane-like isolated pillars. The solid-solution EuSrZnSnAs (0 < < 10) is found to crystallize in the commensurately modulated 3 space group, related to the parent phase but lacking the mirror symmetry. EuZnSnAs orders with a saturation plateau at 1 T for 7 of the 11 Eu cations ferromagnetically coupled (5 K) and shows colossal magnetoresistance at 15 K. The magnetic properties of EuZnSnAs are investigated at higher fields, and the ferromagnetic saturation of all 11 Eu cations occurs at ∼8 T. The temperature-dependent magnetic properties of the solid solution were investigated, and a nontrivial structure-magnetization correlation is revealed. The temperature-dependent Eu and Sn Mössbauer spectra confirm that the europium atoms in the structure are all Eu and that the tin is consistent with an oxidation state of less than four in the intermetallic region. The spectral areas of both Eu(II) and Sn increase at the magnetic transition, indicating a magnetoelastic effect upon magnetic ordering.