Evidence of Local Structural Variations and Their Influence on Magnetic Properties in Mn- and Cr-Containing...

Area of Science:

• Materials Science
• Solid State Chemistry
• Condensed Matter Physics

Background:

• Alloying is a traditional method for improving material properties.
• High-entropy oxides (HEOs) are multicomponent systems with tunable and superior properties compared to single-component oxides.

Purpose of the Study:

• To investigate the local structural and chemical differences between Mn-alloyed and Cr-alloyed HEOs.
• To understand how these differences influence the magnetic properties of the HEOs.

Main Methods:

• Synthesis of six-component (Mg,Co,Ni,Cu,Zn,Mn)O and (Mg,Co,Ni,Cu,Zn,Cr)O thin films.
• Characterization using scanning/transmission electron microscopy (S/TEM).
• Analysis of chemical states using electron energy loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS).
• Validation through density functional theory (DFT) calculations for cation site preference.

Main Results:

• The Mn-alloyed HEO exhibited higher exchange bias and magnetic frustration than the Cr-alloyed HEO.
• S/TEM revealed a mixed rock salt and spinel-like phase in the Mn-alloyed film, contrasting with the single-phase rock salt structure in the Cr-alloyed film.
• EELS and XAS confirmed mixed-valence states of Co and Mn in the Mn-containing HEO.

Conclusions:

• The observed differences in phase structure, cation valences, and site occupations significantly alter the properties of HEOs.
• Mn alloying in HEOs leads to enhanced magnetic properties and complex phase formation.
• Understanding local chemistry and structure is crucial for tailoring HEO properties.