Tilted antiferromagnetic ordering of Mn in Nd_0.62Ca _0.38MnO₃

The magnetic ordering of the Mn spins in polycrystalline Nd _0.62Ca_0.38MnO₃ has been investigated by means of neutron diffraction and ac magnetic susceptibility measurements. Three peaks around 230, 90, and 40 K were observed in the temperature dependence of the in-phase component of the ac susceptibility, χ′(T). Neutron diffraction measurements show that the peak at 90 K is associated with the ordering of the Mn spins, and that at 40 K is due to the reorientation of the Mn spins. Both ferromagnetic and antiferromagnetic coupling between the Mn spins were observed. The spins order at T_N≈130K, with a spin structure consisting of ferromagnetically coupled, tilted antiferromagnetic sheets. No evidence was found from the neutron diffraction data to indicate that the peak around 230 K in ≈′(T) is of magnetic origin, which suggests that it is associated with charge ordering.