Electronic structure evolution in a Eu-based intermetallic system with competing ferro- and antiferro-type exchange interactions

The magnetism in rare-earth intermetallic materials often exhibits complicated behavior due to the multiple exchange mechanisms involving localized 4f and conduction electrons. Understanding the electronic responses in these systems is crucial for clarifying different flavors of quantum magnetism and controlling spin and charge degrees of freedom for purposes such as information storage and energy conversion. Here, in the quaternary intermetallic system EuRhAl₄Si₂, we reveal evident temperature-dependent electronic structure evolutions across the magnetic phase transitions via angle-resolved photoemission spectroscopy. Such alterations in the electronic band dispersions are captured by our density functional theory (DFT) + U calculations considering the experimental magnetic structure and can be understood as arising dominantly from the exchange field effects on the Si 3p orbitals. Further, we provide estimate of the exchange interactions based on our DFT + U calculations. Our results yield a solid understanding on the interplay between the electronic band structure and the collinear magnetism in EuRhAl₄Si₂, while shedding light on the different contributing exchange channels such as the Ruderman-Kittle-Kasuya-Yosida type and the superexchange interactions.