Rare-earth (RE) nanolaminates Mo4RE4Al7C3 featuring ferromagnetism and mixed-valence states

Rare-earth-based (RE) nanolaminates have attracted attention recently because of their complicated magnetism and their potential as precursors for strongly correlated two-dimensional materials. In this work, we synthesized a class of nanolaminates with a $\mathrm{M}{\mathrm{o}}_{4}\mathrm{R}{\mathrm{E}}_{4}\mathrm{A}{\mathrm{l}}_{7}{\mathrm{C}}_{3}$ chemistry, where RE = Ce or Pr. Powder samples of both phases were characterized with respect to structure and composition. Single crystals of $\mathrm{M}{\mathrm{o}}_{4}\mathrm{C}{\mathrm{e}}_{4}\mathrm{A}{\mathrm{l}}_{7}{\mathrm{C}}_{3}$ were used for magnetization measurements. The crystal structure was investigated by means of x-ray diffraction and scanning transmission electron microscopy. Magnetization analysis reveals a ferromagnetic ground state with a Curie temperature of $\ensuremath{\sim}10.5$ K. X-ray absorption near-edge structure provides experimental evidence that Ce is in a mixed-valence state. X-ray magnetic circular dichroism shows that only the Ce atoms with $4{f}^{1}$ configuration occupying one of the two possible sites are ferromagnetically coupled, with a saturation moment of $\ensuremath{\sim}1.2\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}$ per atom. We thus classify $\mathrm{M}{\mathrm{o}}_{4}\mathrm{C}{\mathrm{e}}_{4}\mathrm{A}{\mathrm{l}}_{7}{\mathrm{C}}_{3}$ as a ferromagnetic, mixed-valence compound.