Effects of Band Filling on Magnetic Structures: The Case ofRNi2Ge2

Abstract

We establish that strong Fermi surface nesting drives the N\'eel transition in the $R{\mathrm{Ni}}_{2}{\mathrm{Ge}}_{2}$ compounds. Generalized susceptibility, ${\ensuremath{\chi}}_{0}(\mathbf{q})$, calculations found nesting to be responsible for both incommensurate wave vector, $(000.793)$, in ${\mathrm{GdNi}}_{2}{\mathrm{Ge}}_{2}$, and the commensurate structure, $(001)$, in ${\mathrm{EuNi}}_{2}{\mathrm{Ge}}_{2}$, as revealed by x-ray resonant exchange scattering. A continuous transition from incommensurate to commensurate magnetic structures via band filling is predicted. The surprisingly higher ${T}_{N}$ in ${\mathrm{EuNi}}_{2}{\mathrm{Ge}}_{2}$ than that in ${\mathrm{GdNi}}_{2}{\mathrm{Ge}}_{2}$ is also explained.