Switching on a Spin Glass: Flux Growth, Structure, and Magnetism of La₁₁Mn_{13–<i>x–y</i>}Ni_<i>x</i>Al_<i>y</i>Sn_4−δ Intermetallics

Reactions of tin and manganese in a lanthanum/nickel eutectic melt in alumina crucibles produce La₁₁Mn_{13–<i>x–y</i>}Ni_<i>x</i>Al_<i>y</i>Sn_4−δ (0 ≤ <i>x</i> ≤ 3.6; 2.5 ≤ <i>y</i> ≤ 4.9; 0.6 ≤ δ ≤ 1.1) phases with the stoichiometry dependent on the reactant ratio. These compounds crystallize in a new tetragonal structure type in space group <i>P</i>4<i>/mbm</i>, with <i>a</i> = 8.4197(1) Å, <i>c</i> = 19.2414(3) Å, and <i>Z</i> = 2 for La₁₁Mn_8.2Ni_0.8Al₄Sn_3.3. The structure can be viewed as an intergrowth between La₆Co₁₁Ga₃-type layers and Cr₅B₃-type La/Sn slabs. This system represents a unique playground to study the itinerant magnetism of diluted icosahedral Mn layers. The dilution of manganese sites in the Mn/Ni/Al layer with nonmagnetic elements has a significant effect on magnetic properties, with low Mn content analogues being paramagnetic and higher Mn content analogues such as La₁₁Mn₁₀Al₃Sn_3.4 exhibiting spin-glass behavior with a freezing transition at 20 K. The lack of long-range magnetic ordering is confirmed by heat capacity and resistivity measurements