Magnetic structures of the iridium-based double perovskites Pr2NiIrO6 and Nd2NiIrO6 reinvestigated using neutron diffraction

The magnetic structures of the double perovskites Pr2NiIrO6 and Nd2NiIrO6 have been reinvestigated using high-intensity neutron power diffraction and compared with previously published results by Kayser et al. [Acta Mater. 207, 116684 (2021)10.1016/j.actamat.2021.116684] and Ferreira et al. [Phys. Rev. Mat. 5, 064408 (2021)10.1103/PhysRevMaterials.5.064408]. The strongly enhanced statistics of neutron diffraction data used in this paper help us to disentangle the complicated coexisting magnetic orderings of the three sublattices in Pr2NiIrO6 and Nd2NiIrO6. A mainly ferrimagnetic ordering with additional antiferromagnetic components with propagation vector k=0 has been confirmed in both Pr2NiIrO6 and Nd2NiIrO6 compounds below the magnetic orderings TC=110 and 120 K, respectively. Nd2NiIrO6 further undergoes a second magnetic transition from a ferrimagnet with k=0 to an antiferromagnetic state with k= (12, 12, 0) below TN=15K. A partial persistence of the k=0 type order leads, however, to a coexistence of both magnetic phases below TN not detected previously. The coexistence points to the energies of the magnetic ground states being very similar. Ordered magnetic moments of Ir4+ amounting at 1.5 K to ∼0.6μB in Pr2NiIrO6 and 0.4μB in Nd2NiIrO6 are clearly detected and are compared with the expected value for the Jeff= 12 model.