Interplay of electronic, magnetic, and structural properties of GdB6 from first principles

Gadolinium hexaboride $({\mathrm{GdB}}₆)$ is a well-known field emitter material that has been investigated for more than three decades. We perform a systematical density-functional theory study of ${\mathrm{GdB}}₆$ by using the generalized-gradient approximation and considering the electron interaction parameter $U$. The basic structural and electronic properties are carefully revised, as well as a strong $U$-value dependence in determining the antiferromagnetic (AFM) magnetic structures of Gd $4f$ electronic states. We found a small $U\phantom{\rule{4pt}{0ex}}(0\ensuremath{\sim}3$ eV) showing the most consistent experimental ground-state properties, which gives rise to a magnetic structure with a ground state of C-AFM and a second stable E-AFM. Moreover, we find the distortion modes of boron octahedron play an important role in the interaction between spin and lattice structures in this system. These results will deepen our understanding of the boron-based correlated rare earth compounds.