Incommensurately modulated charge-density wave phase transition in EuAl₂Ga₂

Abstract

Rare-earth-based intermetallics show superconductivity, magnetic order, and heavy fermionic behaviour due to 4f electrons [1]. In Eu-based intermetallics, Eu offers two types of valance states of Eu 2+ (magnetic) and Eu 3+ (nonmagnetic) due to an unstable 4-f shell. EuAl 4 shows the charge density wave (CDW) at T CDW = 140 K and orders antiferromagnetically below T N = 15.4 K; however, EuGa 4 represents the characteristic of CDW above 1GPa, not at ambient pressure, and orders antiferromagnetically below T N = 16.4 K [2], [3]. A recent study on EuAl 2 Ga 2 shows an outof-plane CDW below ∼ 51 K while the magnetic propagation vector lies in-plane below T N = 19.5 K [4]. The present study reports on the incommensurately modulated charge density wave in EuAl 2 Ga 2 . We have performed a Single-crystal X-ray diffraction (SXRD) experiment at beamline P24 of PETRA-III at DESY (Hamburg, Germany) in the temperature range of 300 K -20 K. EuAl 2 Ga 2 possesses tetragonal symmetry with space group I4/mmm at room temperature. Temperature-dependent SXRD experiment reveals the presence of satellite reflections below T CDW with a 1-D modulation vector (0, 0, 0.113). These satellites are used to study the incommensurately modulated charge density wave transition in the material. Our recent study on EuAl 4 shows the tetragonal to incommensurately modulated orthorhombic CDW phase transition [5]. We will present the CDW modulated crystal structure as a function of temperature in EuAl 2 Ga 2 .