Direct hybridization gap from intersite and onsite electronic interactions in CeAg₂Ge₂.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• Antiferromagnetic ordering in intermetallic compounds is crucial for understanding magnetic phenomena.
• Cerium-based compounds often exhibit complex electronic and magnetic behaviors due to localized f-electrons.

Purpose of the Study:

• To elucidate the roles of intersite and onsite interactions in the antiferromagnetic ordering of CeAg2Ge2.
• To investigate the relationship between electronic structure, crystal structure, and magnetic properties.

Main Methods:

• Electronic structure calculations (e.g., DFT).
• Crystal structure analysis.
• Magnetovolume effect measurements.
• Angle-resolved photoemission spectroscopy (ARPES).

Main Results:

• Observed a prominent magnetovolume effect with negative thermal expansion in CeAg2Ge2.
• Identified a direct hybridization gap with a V-shaped band in ARPES data, indicating spin-polarized states.
• Found evidence of strong Ce-Ge hybridization and valence band broadening at low temperatures.

Conclusions:

• Intersite interactions at high temperatures stabilize onsite interactions at low temperatures, driving spin density wave antiferromagnetism.
• Itinerant electron magnetism is responsible for the observed magnetovolume effect and negative thermal expansion.
• The electronic structure, particularly the hybridization gap, is intrinsically linked to the magnetic ordering in CeAg2Ge2.