Crystal Structures and Magnetic Properties of New Europium Melilites Eu₂MSi₂O₇ (M = Mg, Mn) and Their Strontium Analogues

Abstract

Synthesis, crystal structures, and magnetic properties of melilite-type oxides A(2)MSi(2)O(7) (A = Sr, Eu; M = Mg, Mn) were investigated. These compounds crystallize in the melilite structure with space group P4̅2(1)m. The (151)Eu Mössbauer measurements show that the Eu ions are in the divalent state. The Eu(2)MgSi(2)O(7) is paramagnetic down to 1.8 K. Long-range antiferromagnetic ordering is observed at 3.4 K for Sr(2)MnSi(2)O(7). On the other hand, the Eu(2)MnSi(2)O(7) shows a ferrimagnetic transition at 10.7 K. From the magnetization and specific heat measurements, it is found that the Eu(2+) (14 μ(B)) and Mn(2+) (5 μ(B)) sublattices order antiferromagnetically. This result indicates that an interaction between f-d electrons (Eu-Mn) predominantly operate in this compound.