Electronic properties of α-UH₃ stabilized by Zr

Area of Science:

• Materials Science
• Solid State Physics
• Magnetism

Background:

• Uranium hydride (UH₃) exists in different phases, notably α-UH₃ and β-UH₃.
• Understanding the properties of pure UH₃ phases is crucial for applications and fundamental research.
• Previous studies on UH₃ mixtures often showed complex magnetic transitions.

Purpose of the Study:

• To synthesize pure α-UH₃ without β-UH₃ admixture.
• To characterize the structural, thermal, magnetic, and electronic properties of the synthesized material.
• To investigate the influence of zirconium (Zr) doping on these properties.

Main Methods:

• High-pressure hydrogenation of body-centered cubic (bcc) uranium stabilized by zirconium.
• Characterization using magnetic property measurements, specific heat analysis, and electrical resistivity.
• Fully relativistic electronic structure calculations.

Main Results:

• Successfully prepared pure α-UH₃, denoted as (UH₃)₁₋ₓZrₓ, stable in air.
• Observed hydrogen release between 400-450 °C.
• Identified a ferromagnetic ground state with a Curie temperature (T<0xE1><0xB5><0xA_>) of approximately 180 K and uranium (U) moments of 1.0 μB.
• Measured a large spontaneous magnetostriction (ω<0xE2><0x82><0x9B>) of 3.2×10⁻³, linked to spin moment increase.
• Electronic properties were found to be similar to β-UH₃ despite structural differences.

Conclusions:

• Pure α-UH₃ can be synthesized and is stable under ambient and elevated temperatures.
• The material exhibits distinct ferromagnetic behavior and significant magnetostriction.
• Zr doping has a weak, non-monotonic effect on the Curie temperature.
• Electronic properties are largely independent of the crystal structure, suggesting a robust electronic configuration.