The solid solution $\mathrm{Eu}{\left({\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\right)}_4$ was grown in single crystal form to reveal a rich variety of crystallographic, magnetic, and electronic properties that differ from the isostructural end compounds ${\mathrm{EuGa}}_4$ and ${\mathrm{EuAl}}_4$, despite the similar covalent radii and electronic configurations of Ga and Al. Here we report the onset of magnetic spin reorientation and metamagnetic transitions for $x=0–1$ evidenced by magnetization and temperature-dependent specific heat measurements. $T_{\mathrm{N}}$ changes nonmonotonously with $x$, and it reaches a maximum around 20 K for $x=0.50$, where the $a$ lattice parameter also shows an extreme (minimum) value. Anomalies in the temperature-dependent resistivity consistent with charge density wave behavior exist only for $x=0.50$ and 1. Density functional theory calculations show increased polarization between the Ga-Al covalent bonds in the $x=0.50$ structure compared to the end compounds, such that crystallographic order and chemical pressure are proposed as the causes of the charge density wave behavior.

• Received 4 April 2018

DOI:https://doi.org/10.1103/PhysRevB.97.195146