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Structural phase transitions in EuFe2As2 superconductor at low temperatures and high pressures.
Walter O Uhoya1, Georgiy M Tsoi, Yogesh K Vohra
1Department of Physics, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA.
Summary
Researchers investigated the crystal structure of Europium Iron Arsenide (EuFe2As2) under extreme pressure and low temperatures. They observed distinct structural phase transitions, including a suppressed orthorhombic phase and a collapsed tetragonal phase, revealing minimal thermal expansion at high pressures.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Crystallography
Background:
- Europium Iron Arsenide (EuFe2As2) is a material exhibiting complex structural and electronic properties.
- Understanding its behavior under extreme conditions is crucial for fundamental science and potential applications.
Purpose of the Study:
- To investigate the crystal structure of EuFe2As2 under high pressure (up to 35 GPa) and low temperature (down to 8 K).
- To identify and characterize structural phase transitions and their dependence on pressure and temperature.
Main Methods:
- Temperature-dependent X-ray diffraction (XRD) was employed.
- Experiments were conducted using a diamond anvil cell (DAC) at a synchrotron source.
Main Results:
- A phase transition from tetragonal (I4/mmm) to orthorhombic (Fmmm) was observed around 120 K at 4.3 GPa.
- At 10 K, increasing pressure led to the suppression of the orthorhombic phase and the emergence of a collapsed tetragonal phase (I4/mmm) at 11 GPa.
- The collapsed tetragonal phase exhibited an identical pressure-volume (P-V) equation of state at ambient and low temperatures.
Conclusions:
- The high-pressure collapsed tetragonal phase of EuFe2As2 demonstrates a negligible thermal expansion coefficient.
- Structural transitions in EuFe2As2 are sensitive to both pressure and temperature, with distinct phases appearing under varying conditions.
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