Orbital ordering inNdNiO3andSmNiO3investigated by …

International audienceA Mössbauer study of 57Fe doped NiIII perovskites, NdNi0.98Fe0.02O3 and SmNi0.98Fe0.02O3, in the magnetic ordering domain (T≪TN) has revealed that the Fe probes occupy two types of sites, i.e., Fe(1) and Fe(2), showing very different values of the magnetic hyperfine fields (H1≈430-450kOe,H2≈15-22kOe). The close values of the isomer shift (δ) and the second-order quadrupole perturbation parameter (ɛ) in the subspectra, for both Fe sites, have underlined that all the Fe sites are crystallographically equivalent. In the light of orbital ordering model suggested by the neutron diffraction studies, the partial substitution of NiIII (t2g6eg1) by Fe3+ (t2g3eg2) may induce significant topological frustration of Fe3+ spins in surroundings of NiIII orbitals, leading to two different magnetic environments around Fe below TN. Additionally, the Mössbauer spectra at 300 K (>TN) indicate that all the available sites for probe atoms are crystallographically equivalent in the insulating SmNi0.98Fe0.02O3 as well as in the metallic NdNi0.98Fe0.02O3. The present result may be an evidence of the important role of the orbital ordering in determining the electronic properties of the NiIII perovskites containing large rare earth