Continuous Evolution of Eu²⁺/Eu³⁺ Mixed Valency Driven by Pressure and Temperature.

Area of Science:

• Condensed matter physics
• Materials science
• Inorganic chemistry

Background:

• Europium (Eu) compounds are known for their interesting magnetic and electronic properties due to mixed valency.
• Eu4Bi6Se13 crystallizes in a monoclinic structure (P21/m) with linear chains of Eu atoms along the b-axis.

Purpose of the Study:

• To investigate the conditions under which continuous mixed valency occurs in Eu4Bi6Se13.
• To understand the structural and electronic transitions associated with pressure and temperature changes.

Main Methods:

• Magnetic susceptibility measurements (parallel and perpendicular to the b-axis) analyzed with Curie-Weiss theory.
• High-pressure partial fluorescence yield (PFY) X-ray absorption spectroscopy (XAS).

Main Results:

• Applied pressure or reduced temperatures induce a continuous mixed valency state in Eu4Bi6Se13.
• The trivalent Europium (Eu3+) configuration is increasingly favored as pressure increases or temperature decreases.
• Structural and magnetic data support the transition towards a more trivalent state.

Conclusions:

• Eu4Bi6Se13 exhibits pressure- and temperature-induced valence transitions.
• The material's mixed-valent nature is tunable, offering potential for novel electronic applications.