Magnetic ordering of Mn in Ca-doped NdMnO3

We have performed neutron diffraction measurements on polycrystalline Ca-do ped NdMnO3. Magnetic ordering of the Mn spins and spin reorientation were o bserved for all the three compounds studied. Both ferromagnetic and antifer romagnetic couplings between the Mn spins were found, that result in a non- collinear magnetic structure for the Mn spins and suggesting the existence of a close competition between the double exchange and superexchange intera ctions. The ordering temperature shifts to a higher temperature as the Ca c oncentration is increased, while the size of the moment remains basically u naffected. (C) 2000 Elsevier Science B.V. All rights reserved.