Magnetic structure and spin reorientation of the Mn ions in NdMnO3

The crystal structure and magnetic ordering of the Mn spins in polycrystalline ${\mathrm{NdMnO}}_{\mathrm{3}}$ have been investigated by means of neutron diffraction and ac magnetic susceptibility measurements. The compound crystallizes into an orthorhombic symmetry of space group Pbnm. Three peaks were observed in the temperature dependence of the in-phase component of the ac susceptibility, ${\chi }^{\prime }\mathrm{(T).}$ Neutron diffraction measurements show that all three peaks observed in ${\chi }^{\prime }\mathrm{(T)}$ are of magnetic origin, and are associated with the ordering and the reorientation of the Mn spins. Both ferromagnetic and antiferromagnetic couplings between the Mn spins were observed, resulting in a noncollinear magnetic structure. The Mn spins order at $T_m\text{≈75}$ K, and the moment saturates at ∼20 K at ${\mathrm{〈\mu }}_z{\text{〉=2.21\hspace{0.5em}μ}}_B.$