Multinary Intermetallics from Molten Al. Synthesis of SmNiAl₄Ge₂and YNiAl₄Ge₂. Possible Spin Frustration in Separated Triangular Sm³⁺Layers

Abstract

SmNiAl 4 Ge 2 crystallizes from molten Al containing Sm, Ni, and Ge. The compound crystallizes in the rhomohedral space group R 3 m with a = 4.1121(6) Å, c = 31.109(6) Å, and V = 455.5(1) Å 3 . The YNiAl 4 Ge 2 analogue is also stable. The crystal structure consists of layers of [NiAl 4 Ge 2 ] 3- separated by monolayers of hexagonally close-packed Sm 3+ ions. The Ni atoms are surrounded by eight Al atoms in the structure. Each Sm atom has an octahedral environment of six Ge atoms. The magnetism of SmNiAl 4 Ge 2 is unusual, possibly reflecting the presence of geometrical spin frustration. The magnetization exhibits a well-defined hysteresis loop, without signs of ferromagnetism. It also exhibits irreversibility in the field-cooled and zero-field-cooled magnetization but without the typical characteristic spin glass behavior.