Uniform chemical pressure effect in solid solutions Ba(1-x)Sr(x)Fe2As2 and Sr(1-x)Ca(x)Fe2As2

TL;DR

This study investigates how substituting alkaline earth elements in Fe2As2 compounds induces a uniform chemical pressure, affecting structural parameters systematically across different compositions.

Contribution

It provides detailed structural analysis showing a monotonic change in lattice parameters consistent with Vegard's law, highlighting a continuous chemical pressure effect in these solid solutions.

Findings

Lattice parameters decrease monotonically with substitution.

The c/a ratio and unit cell volume follow Vegard's law.

Chemical pressure increases continuously across the phase diagram.

Abstract

The effect of alkaline earth substitution on structural parameters was studied in high-quality single crystals of Ba(1-x)Sr(x)Fe2As2 and Sr(1-x)Ca(x)Fe2As2 grown by the self-flux method. The results of single-crystal and powder x-ray diffraction measurements suggest a continuous monotonic decrease of both a- and c-axis lattice parameters, the c/a tetragonal ratio, and the unit cell volume with decreasing alkaline earth atomic radius as expected by Vegard's law. As a result, the system experiences a continuously increasing chemical pressure effect in traversing the phase diagram from x=0 in Ba(1-x)Sr(x)Fe2As2 to x=1 in Sr(1-x)Ca(x)Fe2As2.