Neutron-diffraction study of the magnetic ordering in superconducting NdRh4B4

The results of neutron-diffraction measurements are reported which confirm the development of long-range magnetic order in superconducting Nd${\mathrm{Rh}}_4$ ${\mathrm{B}}_4$. Two distinct antiferromagnetic transitions occur below the superconducting phase-transition temperature $T_{\mathrm{SC}}=5.4\mathrm{}$ K, one at $T_{\mathrm{MH}}\simeq 1.5$ K and the other at $T_{\mathrm{ML}}\simeq 1.0$ K. In both phases, the body-centered tetragonal sublattice of Nd atoms orders antiferromagnetically with the ${\mathrm{Nd}}^{3+}$ moments aligned along the unique $c$ axis. The magnetic moment is modulated sinusoidally along the [100] direction in the higher-temperature magnetic phase and along the [110] direction in the lower-temperature phase. The measured saturation moment is 3.4± 0.5${\mathrm{\mu }}_{\mathit{B}}$. No ferromagnetic component could be detected in the higher-temperature magnetic phase within an experimental sensitivity of 0.3${\mathrm{\mu }}_{\mathit{B}}$.