Magnetic moment induced by orbital hybridization in square net EuRhAl4Si2

Square-net lattice materials are known for hosting diverse and intriguing physical properties, from real and reciprocal-space topology to unique electronic behaviors protected by symmetry. These properties are achieved even without geometric frustration or anisotropic interactions, making them attractive candidates for studying unconventional magnetic states. EuRhAl₄Si₂ is a square-net antiferromagnet with T_N = 11.4 K. Magnetization isotherms in the AFM state display a 1/3 magnetization (M) step, associated with a “up-up-down” Eu moment configuration. In addition, we find two additional much smaller steps (“-/+m”) at the 1/3M plateau, where m is a small induced moment (m<<M). In this talk, I will discuss the magneto-transport properties, ARPES measurements, neutron diffraction and DFT calculations for EuRhAl₄Si₂, aimed at identifying the mechanism for the small induced moment m. Our measurements reveal a pronounced hybridization gap (>100 meV) below the Fermi level that opens up in the magnetically-ordered state. This gap, resulting from Eu f- and Si p-orbital hybridization, is intricately tied to the observed magnetization steps and the unique magnetic ground state, as determined by neutron diffraction. DFT calculations quantify the orbital hybridization responsible for these effects and help clarify the interaction types driving the unique magnetic and electronic response.