Charge density wave behavior and order-disorder in the antiferromagnetic metallic series Eu(Ga_1-xAl_x)_4

TL;DR

This study explores the complex crystallographic, magnetic, and electronic behaviors in the Eu(Ga_1-xAl_x)_4 series, revealing charge density waves, magnetic reorientations, and structural changes driven by chemical composition and order.

Contribution

It reports the discovery of charge density wave behavior and magnetic reorientation phenomena in Eu(Ga_1-xAl_x)_4, highlighting the role of crystallographic order and chemical pressure.

Findings

Charge density waves observed at x=0.50 and 1.

Non-monotonous variation of T_N with x.

Magnetic spin reorientation and metamagnetic transitions.

Abstract

The solid solution Eu(Ga_1-xAl_x)_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 EuGa_4 and 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_N changes non-monotonously 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 for x = 0.50 and 1 only. 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.