The modulated structures of La_2–x Pr _x O₂MnSe₂ (0 ≤ x ≤ 1) and La_2–x Nd _x O₂MnSe₂ (0 ≤ x ≤ 0.6)

Abstract

Abstract The solid solutions La 2– x Pr x O 2 MnSe 2 (0≤ x ≤1) and La 2– x Nd x O 2 MnSe 2 (0≤ x ≤0.6) were synthesized in a NaI/KI flux between 800 and 900°C. The selenide oxides adopt a ZrCuSiAs-related structure with modulated [MnSe 2 ] 2– -layers which consist of a mixture of edge- and corner-sharing MnSe 4/2 -tetrahedra. The crystal structures are described with a (3+1)D model in superspace group Cmme ( α 0½)0s0. The modulation vector q can be controlled by partial substitution of La 3+ for Pr 3+ and Nd 3+ via the unit cell volume leading to, amongst others, (La 0.55 Pr 0.45 ) 2 O 2 MnSe 2 with α =1/6, which allows the projection onto 3D space by using a simple sixfold a axis.