From localized 4f electrons to anisotropic exchange interactions in ferromagnetic CeRh6Ge4

CeRh6Ge4 is a cerium-based ferromagnetic material exhibiting a quantum critical behavior under pressure. We derive effective exchange interactions, using the framework of density functional theory combined with dynamical mean-field theory. Our results reveal that the nearest-neighbor ferromagnetic interaction along the c axis is isotropic in spin space, leading to a formation of spin chains. On the other hand, the inter-chain coupling is highly anisotropic: The in-plane moment weakly interacts ferromagnetically in the a–b plane to stabilize the ferromagnetic state, whereas the z-component couples antiferromagnetically, contributing to its destabilization. The magnetic anisotropy of the interchain interactions as well as of the local 4f wavefunctions characterizes the magnetic properties underlying the ferromagnetic transition and the quantum critical behavior in CeRh6Ge4. CeRh6Ge4, a cerium-based ferromagnetic material, exhibits quantum critical behavior under pressure, posing intriguing questions about its magnetic interactions. Here, the authors use density functional theory combined with dynamical mean-field theory to reveal the formation of isotropic spin chains along the c axis that are coupled by anisotropic inter-chain interactions, elucidating the material’s ferromagnetic transition and quantum criticality.