Abstract
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 AlB2-type structure with space group 𝑃6/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 𝑇Curie=25.8K. The susceptibility follows the Curie-Weiss law at high temperatures, which allowed us to determine the paramagnetic Curie temperature 𝜃𝑃=36.2(1)K and an effective magnetic moment 𝜇eff=8.07(1)µ𝐵/Eu. This value is in agreement with the theoretical value of 7.9µ𝐵 for Eu2+ free ion. Moreover, we have prepared the Eu1−𝑥Sr𝑥AlSi 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 Eu1−𝑥Sr𝑥AlSi 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 𝜇eff and 𝑇Curie. Long-range magnetic order in Eu1−𝑥Sr𝑥AlSi persists up to 𝑥=0.95, whereas superconductivity is only observed for samples with 𝑥>0.97.
