Symmetry consideration and eg bands in NdNiO 3 and YNiO 3

Abstract

Group theoretical analyses are applied to the magnetic and electronic structures of NdNiO 3 and YNiO 3, whose electronic structures have been studied very recently by the LSDA+U method. The space groups of the crystallographic structure of these materials are Pbnm and P2 1/ n, respectively [Phys. Rev. B 46 (1992) 4414; Phys. Rev. Lett. 82 (1999) 3871]. There are no Jahn–Teller distortion modes consistent with observed propagation vector of spin polarized neutron-diffraction. Two possible spin configurations (magnetic space groups) C a mc2 1 and P b a are derived from Pbnm for NdNiO 3. Then the electronic structures with each symmetry are studied by using the tight-binding model. Clear separation of partial density of states exists in P b a but does not in orthorhombic C a mc2 1. The combination of results of the present work and the previous LSDA+U calculation shows that the ground state magnetic structure of NdNiO 3 is monoclinic P b a. NdNiO 3 has only one kind of Ni sites, while YNiO 3 has two inequivalent Ni sites. The magnetic structure of YNiO 3 is monoclinic P b 2 1/ a, if one assumes no magnetic moment on Ni ions (Ni 4+) on one of these inequivalent sites.