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 R3m 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 ] 3separated 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 fieldcooled and zero-field-cooled magnetization but without the typical characteristic spin glass behavior.

Sm2NiSn4: The intermediate structure type between ZrSi2 and CeNiSi2

“…However, the Ni d orbitals are almost fully occupied with eletrons below the Fermi level, indicating a reduced state for Ni(1) atom. This is reasonable, as is well known that, in many intermetallic phases containing late transition metals with high electronegativity, band structure calculations suggest the transition metals are effectively in neutral or negative oxidation states [11,27]. Semi-empirical COOP allows a more quantitative bond analysis.…”

Quaternary Germanides Formed in Molten Aluminum: Tb2NiAl4Ge2 and Ce2NiAl6-xGe4-y (x ∼ 0.24, y ∼ 1.34)Dedicated to Professor Welf Bronger on the Occasion of his 70th Birthday

“…With the field oriented perpendicular to the c-axis, i.e. in the abplane, the compound exhibits a µ eff of 9.77 µ B and a θ of Ϫ21.6 K. The µ eff values are very close to the theoretical magnetic moment for Tb 3ϩ of 9.72 µ B [19], indicating that Ni is diamagnetic as is the case in other transition metal aluminum compounds [2,3]. Well below the transition temperature, at~5 K, the magnetization curve shows a linear increase with increasing field up to 55,000 G with no indications of magnetic saturation, see Figure 7b.…”

“…Based on the Tb yields for this reaction were on the order of 80%. Reaction attempts without excess Al did not produce pure product but instead mixtures of phases including TbNiAl 4 Ge 2 [3] and Tb 2 NiAl 4 Ge 2 .…”

“…Tb 2 NiAl 4 Ge 2 zeigt Curie-Weiss paramagnetisches Verhalten mit einem antiferromagnetischen Übergang bei ഠ20 K. Ce 2 NiAl 6Ϫx Ge 4Ϫx zeigt ein sehr viel komplexeres magnetisches Verhalten, wahrscheinlich aufgrund von temperaturinduzierten Änderung der Valenz des Ce-Atoms. containing compounds including Sm 2 Ni(Si 1-x ,Ni x )Al 4 Si 6 [2], RENiAl 4 Ge 2 (RE ϭ Sm, Tb, Y) [3], RE 2 Fe(Fe,Si)Al 3 Si 4 (RE ϭ Ce, Pr, Nd, Sm) [4], REFe 4 Al 9 Si 6 (RE ϭ Tb, Er) [5], RE 8 Ru 12 Al 49 Si 9 (Al x Si 12-x ) (RE ϭ Sm and Pr) [6] and RE 2 Al 3 Si 2 (RE ϭ Ho, Er, Tm) [1a]. In addition to being of basic scientific interest complex intermetallics of Al are of interest to applied metallurgy due to their compositional relationships to aluminum matrix composites [7].…”

Quaternary alumogermanides in the Er-{Co,Ni}-Al-Ge systems

“…In the present paper we report on the formation of two new alumogermanides, which crystallize with the Tb 2 NiAl 4 Ge 2 [1] and YNiAl 4 Ge 2 [2] structure types, respectively. The crystal structures of these compounds were solved and refined from X-ray single crystal and powder diffraction data from single-phase samples obtained during systematic investigations of the Er-{Co,Ni}-Al-Ge systems [3][4][5].…”