X-ray, magnetization, and Mössbauer studies of new hexagonal compounds $R{\mathrm{Rh}}_6{\mathrm{B}}_4$ ($R=\mathrm{rare}\mathrm{earth}$) were performed. Y${\mathrm{Rh}}_6$${\mathrm{B}}_4$ and Lu${\mathrm{Rh}}_6$${\mathrm{B}}_4$ exhibit strongly enhanced itinerant paramagnetism. La${\mathrm{Rh}}_6$${\mathrm{B}}_4$ and ${\mathrm{Eu}}^{3+}$${\mathrm{Rh}}_6$${\mathrm{B}}_4$ exhibit itinerant-electron ferromagnetism ($T_c=6\mathrm{} \mathrm{and} 19$ K) with large magnetic anisotropy and hysteresis [$H_c\left(\mathrm{Eu}{\mathrm{Rh}}_6{\mathrm{B}}_4\right)=2.1\mathrm{}$ kOe at 4.1 K]. All systems, when doped with 0.5 at.% Fe, show very high Curie points (100 to 300 K) and moments per Fe ion of up to 8${\mathrm{\mu }}_{\mathrm{B}}$.

• Received 21 July 1980

DOI:https://doi.org/10.1103/PhysRevLett.45.2128