Hyperfine interactions in the 13 K ferromagnet Eu 2Si 5N 8

Abstract

Single-phase Eu 2Si 5N 8 was synthesized from metallic europium and silicon diimide in a tungsten crucible using a high-frequency furnace. The Eu 2Si 5N 8 structure consists of a three-dimensional network of corner sharing SiN 4 tetrahedra in which the europium ions occupy two crystallographically different sites. Magnetic susceptibility measurements of Eu 2Si 5N 8 show Curie–Weiss behaviour above 50 K with an experimental magnetic moment of 7.67(5) μ B/Eu, indicating divalent europium. Ferromagnetic ordering is detected at 13.0(5) K. The saturation magnetic moment is 7.0(1) μ B/Eu at 5 T and 4.5 K. The two europium sites could not be distinguished by 151Eu Mössbauer spectroscopy. The room temperature spectrum could be fitted by only one signal at an isomer shift of δ=−11.82(5) mm/ s subject to quadrupole splitting of ΔE Q =16.8(2) mm/ s and an asymmetry parameter of 0.67(7). At 4.2 K full magnetic hyperfine field splitting is observed with a hyperfine field of 24.9(2) T at the europium nuclei.