Neutron Diffraction Studies on DySb, NdSb, and CeSb

Neutron diffraction data from powder samples of $\mathrm{DySb}$ , $\mathrm{NdSb}$ , and $\mathrm{CeSb}$ confirm antiferromagnetic ordering below Néel temperatures of 12, 16, and 18°K. The magnetic cell of $\mathrm{DySb}$ has dimensions twice that of the chemical cell; a possible antiferromagnetic structure has spins ferromagnetically aligned in each (111) magnetic plane with the spins in adjacent (111) planes having opposing directions. The $\mathrm{NdSb}$ magnetic cell has tetragonal symmetry and the same lattice constant as the cubic chemical cell. The antiferromagnetic arrangement has ferromagnetic sheets parallel to the (001) planes with the spin direction [001] alternating from one layer to the next. The ordered moment in $\mathrm{DySb}$ is ${\text{8.9\hspace{0.17em}±\hspace{0.17em}0.3\hspace{0.17em}μ}}_{\mathrm{B}}$ and ${\text{2.8\hspace{0.17em}±\hspace{0.17em}0.2\hspace{0.17em}μ}}_{\mathrm{B}}$ in $\mathrm{NdSb}$ . The $\mathrm{CeSb}$ magnetic reflections can be indexed as a modulated wave propagating along the [110] direction with a wavelength of 2.7a_o or $\text{17.5\hspace{0.17em}±\hspace{0.17em}0.5\hspace{0.17em}Å}$ . All of the $\mathrm{CeSb}$ magnetic reflections do not conform to a simple modulated structure. Assuming a helical spin structure with the spin axis in the [001] direction yields an ordered moment of ${\text{1.9\hspace{0.17em}±\hspace{0.17em}0.2\hspace{0.17em}μ}}_{\mathrm{B}}$ .