Thermal spin fluctuations in CoCrFeMnNi high entropy alloy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• High entropy alloys (HEAs) based on 3d transition metals offer promising magnetic characteristics for advanced technological uses.
• Limited experimental data for single-phase alloys hinders a full understanding of HEA behavior at finite temperatures.

Purpose of the Study:

• Investigate the magnetic structure of polymorphic CoCrFeMnNi in the paramagnetic state.
• Analyze the influence of longitudinal spin fluctuations (LSFs) on magnetic moments and phase stability as a function of temperature.

Main Methods:

• Utilize first-principles alloy theory.
• Incorporate longitudinal spin fluctuations (LSFs) calculations.
• Examine both face-centered cubic (fcc) and hexagonal close-packed (hcp) structures.

Main Results:

• LSFs induce significant magnetic moments in Cobalt (Co), Chromium (Cr), and Nickel (Ni) for both fcc and hcp phases.
• The hexagonal close-packed (hcp) phase is energetically favored over the face-centered cubic (fcc) phase at cryogenic temperatures, leading to negative stacking fault energy.
• Increasing temperature elevates stacking fault energy, consequently reducing the formation of stacking faults and nano-twins.

Conclusions:

• Longitudinal spin fluctuations play a crucial role in determining the magnetic structure and phase stability of CoCrFeMnNi HEAs.
• The temperature-dependent behavior of stacking fault energy influences the microstructural evolution, impacting alloy performance.
• The theoretical predictions align with recent experimental observations, validating the computational approach.