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DOE OSTI2020

Materials Data on Sr(AlSi)2 by Materials Project

Al2Si2Sr crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Sr2+ is bonded to six equivalent Si4- atoms to form SrSi6 octahedra that share corners with twelve equivalent AlSi4 tetrahedra, edges with six equivalent SrSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All Sr–Si bond lengths are 3.18 Å. Al3+ is bonded to four equivalent Si4- atoms to form AlSi4 tetrahedra that share corners with six equivalent SrSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent SrSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedra tilt angles range from 24–50°. There are three shorter (2.54 Å) and one longer (2.60 Å) Al–Si bond lengths. Si4- is bonded to three equivalent Sr2+ and four equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing SiSr3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Sr3(AlSi)2 by Materials Project

Al2Si2Sr3 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Sr sites. In the first Sr site, Sr is bonded to eight equivalent Al and four equivalent Si atoms to form a mixture of face and edge-sharing SrAl8Si4 cuboctahedra. All Sr–Al bond lengths are 3.45 Å. All Sr–Si bond lengths are 3.62 Å. In the second Sr site, Sr is bonded in a 7-coordinate geometry to two equivalent Al and five equivalent Si atoms. Both Sr–Al bond lengths are 3.32 Å. There are four shorter (3.32 Å) and one longer (3.38 Å) Sr–Si bond lengths. Al is bonded in a 2-coordinate geometry to six Sr, one Al, and two equivalent Si atoms. The Al–Al bond length is 2.58 Å. Both Al–Si bond lengths are 2.52 Å. Si is bonded in a 2-coordinate geometry to seven Sr and two equivalent Al atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Magnetism in EuAlSi and the Eu 1−𝑥 ⁢Sr 𝑥 ⁢ AlSi solid solution solid solution

The magnetic properties of EuAlSi, a compound comprising a honeycomb lattice of Al/Si atoms and a triangular lattice of Eu atoms, are presented. By means of single-crystal x-ray diffraction, we find that EuAlSi crystallizes in an AlB 2 -type structure with space group 𝑃⁢6/mmm and unit cell parameters 𝑎 = 4.2229⁢ (10) ⁢Å and 𝑐 = 4.5268 ⁢(12)⁢ Å. Our magnetic measurements indicate that EuAlSi is a soft ferromagnetic material with 𝑇 Curie = 25.8 K. The susceptibility follows the Curie-Weiss law at high temperatures, which allowed us to determine the paramagnetic Curie temperature 𝜃 𝑃 = 36.2 ⁢(1) ⁢K and an effective magnetic moment 𝜇 eff = 8.07 ⁢(1)⁢ µ 𝐵 /Eu. This value is in agreement with the theoretical value of 7.9 µ 𝐵 for Eu 2+ free ion. Moreover, we have prepared the Eu 1−𝑥 ⁢Sr 𝑥 ⁢ AlSi solid solution, where the atoms in the triangular lattice were systematically exchanged, in order to study the evolution of the collective quantum properties from the ferromagnetic EuAlSi toward the superconducting SrAlSi. Across the Eu 1−𝑥 ⁢Sr 𝑥 AlSi solid solution, the unit cell parameters change linearly, following Vegard’s law, and making the system reliable for studying composition dependence of the interplay between the crystal structure and physical properties. As the Sr content increases, i.e., 𝑥 increases, we note a consistent reduction of 𝜇 eff and 𝑇 Curie . Long-range magnetic order in Eu 1−𝑥 ⁢Sr 𝑥 ⁢ AlSi persists up to 𝑥 = 0.95, whereas superconductivity is only observed for samples with 𝑥 > 0.97.

Walicka, Dorota I. [University of Geneva (Switzerl↗