Anisotropic Structural and Magnetic Response in Sm2Ir8Al31: Al-Sublattice Reconstruction upon Sm Substitution
Abstract
Chemical pressure plays a critical role in determining the crystal structures and physical properties of intermetallic compounds. Here, we report the synthesis, crystal structure, and physical properties of Sm2Ir8Al31, a structural analog of UIr4Al15, in which the smaller 5f uranium atoms are replaced by larger 4f samarium atoms. Single-crystal X-ray diffraction reveals a tetragonal √2×√2×1 superstructure with space group P4̅21m, derived from a UIr4Al15-like average structure with space group P42/nmc. Comparison with UIr4Al15 shows that chemical pressure from U-to-Sm substitution produces a strongly anisotropic structural response rather than a uniform expansion of the Ir-Al framework. While one Ir coordination environment undergoes only modest changes, the other exhibits substantial local rearrangement. The Al sublattice primarily accommodates these structural distortions, with selected Al sites showing positional splitting, anisotropic atomic displacement ellipsoids, and partial occupancies, resulting in an Al-rich composition of approximately Sm2Ir8Al31. Magnetic susceptibility measurements reveal a direction dependence, including a broad anomaly near 50 K for selected magnetic-field orientations. However, the absence of corresponding anomalies in heat capacity, electrical resistivity, and lattice parameters suggests that this feature is more consistent with an anisotropic magnetic crossover than a bulk thermodynamic phase transition. These results highlight how chemical substitution at the f-element site can induce Al-sublattice reconstruction and modify the magnetic response within a closely related Ir-Al structural framework.
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BibTeX
@misc{xu2026anisotropic,
title = {{Anisotropic Structural and Magnetic Response in Sm$_2$Ir$_8$Al$_31$: Al-Sublattice Reconstruction upon Sm Substitution}},
author = {Mingyu Xu and Weiwei Xie},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36140},
eprint = {2610.36140},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36140},
}
RIS
TY - UNPB
TI - Anisotropic Structural and Magnetic Response in Sm_2Ir_8Al_31: Al-Sublattice Reconstruction upon Sm Substitution
AU - Mingyu Xu
AU - Weiwei Xie
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.36140
UR - https://arxiv.org/abs/2610.36140
AB - Chemical pressure plays a critical role in determining the crystal structures and physical properties of intermetallic compounds. Here, we report the synthesis, crystal structure, and physical properties of Sm_2Ir_8Al_31, a structural analog of UIr_4Al_15, in which the smaller 5f uranium atoms are replaced by larger 4f samarium atoms. Single-crystal X-ray diffraction reveals a tetragonal √2×√2×1 superstructure with space group P4̅2_1m, derived from a UIr_4Al_15-like average structure with space group P4_2/nmc. Comparison with UIr_4Al_15 shows that chemical pressure from U-to-Sm substitution produces a strongly anisotropic structural response rather than a uniform expansion of the Ir-Al framework. While one Ir coordination environment undergoes only modest changes, the other exhibits substantial local rearrangement. The Al sublattice primarily accommodates these structural distortions, with selected Al sites showing positional splitting, anisotropic atomic displacement ellipsoids, and partial occupancies, resulting in an Al-rich composition of approximately Sm_2Ir_8Al_31. Magnetic susceptibility measurements reveal a direction dependence, including a broad anomaly near 50 K for selected magnetic-field orientations. However, the absence of corresponding anomalies in heat capacity, electrical resistivity, and lattice parameters suggests that this feature is more consistent with an anisotropic magnetic crossover than a bulk thermodynamic phase transition. These results highlight how chemical substitution at the f-element site can induce Al-sublattice reconstruction and modify the magnetic response within a closely related Ir-Al structural framework.
ER -