Proton nuclear magnetic resonance line narrowing and tetragonal lattice distortion in SmH 2+ ξ (0 ⩽ ξ ⩽ 0.40)

Abstract

Proton magnetic resonance experiments have been made on samarium hydride samples SmH 2+ξ (0⩽ ξ⩽0.40) to search for proton self-diffusion and hydrogen ordering effects. Data are presented for the linewidths and some line shapes for temperatures from about 78 K to 295 K. For all samples except SmH 2.00, proton line narrowing was observed. However, for ξ=0.30 and ξ=0.40 a system of two lines appeared below about 250 K. One of these lines is broad, and its second and fourth moments exhibit a weak temperature dependence. This indicates a possible hydrogen sublattice ordering below 250 K since this effect may hinder the proton diffusion and thus a broad resonance line results. Our X-ray studies revealed a very small ( c: a≈1.003) tetragonal deformation in SmH 2.30 at low temperatures. The effect was much less distinct in SmH 2.40 and not detected in SmH 2.12.