Optical and magnetic properties of EuSi₂O₂N₂

A new europium-silicon-oxynitride compound EuSi₂O₂N₂ was obtained by a reaction of Eu₂O₃, SiO₂, and α–Si₃N₄ at 1300 °C under a nitrogen atmosphere. EuSi₂O₂N₂ is indexed on a monoclinic unit cell with a = 13.151(5) Å, b =17.311(5) Å, c = 7.956(2) Å, β = 104.12(4)°, and V = 1756.56 ų. EuSi₂O₂N₂ shows a highly pure yellow color associated with a very steep drop in the reflection spectrum with an optical absorption edge at about 512 nm (2.43 eV). On the other hand, EuSi₂O₂N₂ can be efficiently excited in the visible range 370–485 nm and shows a broad band emission peaking at about 568 nm corresponding to the Eu²⁺ 4f⁶5d¹ → 4f⁷ transition. EuSi₂O₂N₂ shows paramagnetic Curie behavior with an experimental magnetic moment of 7.89(3) μ_B in accordance with 7 unpaired spins of Eu²⁺. Additionally, no magnetic ordering can be observed down to 5 K. The divalent nature of the Eu ions in EuSi₂O₂N₂ is evident from both luminescence and magnetic properties.