Magnetic structure of Tb${\mathrm{Ni}}_2$${\mathrm{B}}_2$C

Neutron-diffraction techniques have been used to study the magnetic structure of Tb${\mathrm{Ni}}_2$${\mathrm{B}}_2$C. The measurements, performed on single crystals of this compound, show that below approximately 15 K the moments order in an almost longitudinal spin wave with wave vector along ${\mathbf{a}}^{*}$. The magnitude of the wave vector is close to that obtained in the Ho, Er, and Gd compounds. This observation provides additional evidence that there are common Fermi-surface nesting features along ${\mathbf{a}}^{*}$ in the rare-earth nickel boride carbides which cause the magnetic ordering of the rare-earth moments via the Ruderman-Kittel-Kasuya-Yosida mechanism. Below approximately 8 K, the experimental results indicate the development of a small ferromagnetic component.