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Phase evolution in thermally annealed Ni/Bi multilayers studied by X-ray absorption spectroscopy.
Bidyadhar Das1, Madhusmita Sahoo2, Abhilash Patra1
1School of Physical Sciences, National Institute of Science Education and Research (NISER) Bhubaneswar, HBNI, Jatni, Khurda-752050, Odisha, India. kartik@niser.ac.in.
Physical Chemistry Chemical Physics : PCCP
|February 3, 2022
Summary
X-ray Absorption Spectroscopy (XAS) effectively tracks local bonding changes in NiBi3 and NiBi compounds. This method correlates macroscopic properties with atomic-level diffusion dynamics, proving valuable for studying material transformations.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Surface Science
Background:
- Nickel-bismuth (Ni-Bi) thin films form NiBi3 and NiBi compounds, exhibiting superconductivity and ferromagnetism.
- The formation of these compounds involves slow diffusion, leading to time and temperature-dependent local atomic environments.
- Understanding these local environment changes is crucial for controlling material properties.
Purpose of the Study:
- To evaluate X-ray Absorption Spectroscopy (XAS) as a method for monitoring local bonding environment alterations in NiBi3 and NiBi.
- To investigate the decomposition of NiBi3 under thermal annealing and its impact on structural and magnetic properties.
- To correlate macroscopic material behavior with microscopic structural and electronic changes.
Main Methods:
- Thermal annealing of NiBi3 thin films up to 500 °C to induce changes in the local atomic environment.
- X-ray Absorption Spectroscopy (XAS) to probe the local bonding and electronic structure.
- Magnetic hysteresis measurements to assess magnetic properties and phase dominance.
- Density Functional Theory (DFT) calculations, including Bader charge analysis, to support experimental findings.
Main Results:
- XAS successfully tracked the decomposition of NiBi3 into NiO and Bi upon annealing, consistent with observed structural and magnetic changes.
- Magnetic measurements indicated NiO as the dominant phase (>90%) after annealing at 500 °C, confirmed by XAS.
- A shift in the Ni K-edge observed in annealed samples was attributed to an increased Ni atom charge state, validated by DFT.
Conclusions:
- X-ray Absorption Spectroscopy (XAS) is a reliable tool for studying diffusion dynamics and local environment changes in NiBi3 systems.
- The study successfully correlated macroscopic properties (structural, magnetic) with microscopic bonding environment modifications.
- Findings highlight the utility of XAS in understanding and controlling the behavior of intermetallic compounds during thermal processing.
