Stability of Ni sites across the pressure-induced insulator-to-metal transition in YNiO3

Abstract

The local environment of nickel atoms in Y N iO3 across the pressure-induced insulator to metal (IM) transition was studied using X-ray absorption spectroscopy (XAS) supported by ab initio calculations. The monotonic contraction of the N iO6 units under applied pressure observed up to 13 GPa, stops in a limited pressure domain around 14 GPa, before resuming above 16 GPa. In this narrow pressure range, crystallographic modifications basically occur in the medium/long range, not in the N iO6 octahedron, whereas the evolution of the near-edge XAS features can be associated to metallization. Ab initio calculations show that these features are related to medium range order, provided that the Ni-O-Ni angle enables a proper overlap of the Ni eg and O 2p orbitals. Metallization is then not directly related to modifications in the average local geometry of the N iO6 units but more likely to an inter-octahedra rearrangement. These outcomes provides evidences of the bandwidth driven nature of the IM transition.

Metal-insulator transition in Nd1−xEuxNiO3: Entropy change and electronic delocalization

“…In addition to this, recent XAS measurements in YNiO 3 under P have provided clear evidence that the MI transition is bandwidth-driven and not related to a sudden modification in the local geometry of the NiO 6 octahedra. 24 These results corroborate our findings that the magnetic ordering of the Ni ions has little effect on the MI transition and the entropy released at T MI is mainly due to the electronic delocalization.…”

Rare-earth nickelatesRNiO3: thin films and heterostructures

“…Obradors et al 75 and Canfield et al 76 bar to 30 kbar (= 3 GPa). Later on, similar pressure measurements were performed on more distorted members of the family, such as SmNiO 3 77 and YNiO 3 78,79 . In all investigated cases, increasing the applied pressure results in a decrease of the transition temperature T MI , whereas the room temperature resistivity of the samples remains unchanged.…”

Metastable Materials Accessed under Moderate Pressure Conditions (P ≤ 3.5 GPa) in a Piston-Cylinder Press

“…More results concern (i) the study of magnetic and electronic properties of RNiO 3 (R = Pr, Nd, Eu, Ho and Y) from resonant X-rays [ 26 ]; (ii) the magnetism and magnetic structures of the perovskite series NdNi 1−x Mn x O 3 from neutron powder diffraction [ 27 ]; (iii) Mössbauer results in 57 Fe-doped Ni perovskites combined with neutron studies offering additional evidence of the charge disproportionation in RNiO 3 (R = Tm and Yb) [ 28 ], and allowing us to complete the phase diagram for these materials ( Figure 2 ); (iv) the stability of the Ni sites across the pressure-induced insulator-metal transition in YNiO 3 , previously prepared at 2 GPa [ 29 ]; and (v) the spin-canted magnetism and decoupling of the charge and spin-orbit coupling in NdNiO 3 [ 30 ]. Recently, the extremely high angular resolution of the MSPD diffractometer at ALBA synchrotron X-ray source allowed us to observe the characteristic peak splitting in the (2,2,4) and (-2,2,4) twin reflections in SmNiO 3 ( Figure 2 ), thus confirming the monoclinic distortion and charge disproportionation in this perovskite with Sm 3+ ion with a relatively large size [ 31 ].…”