Structural disorder and magnetic correlations driven by oxygen doping in Nd₂NiO_4.11

Growth and Oxygen Stoichiometry Control of High-Quality La2CoO4+δ Single Crystals (δ = 0.25)

“…Figure 5a shows the existence of an orthorhombic phase (SG: Fmmm) together with a tetragonal one (F4/mmm), as revealed by profile matching using the Fullprof software suite. Refined lattice parameters for the The existence of a monoclinic symmetry has never been reported for LCO, while it is common for oxygen doped Ruddlesden-Popper phases as (Pr/Nd)2NiO4.25, 14,31 and it is presently under investigation. In order to adjust a homogeneous oxygen content over the entire crystal, post-synthesis annealing of the crystal under defined conditions has been carried out.…”

“…long-range oxygen ordering, is consequently added as a fourth degree of freedom to the charge, spin and orbital ordering. 14 Oxygen insertion and related structural and electronic ordering have been much less investigated compared to A-cation type compounds. [15][16][17][18][19] This is essentially related to the fact that adjusting defined oxygen stoichiometries i.e.…”

“…16,[18][19][20][21] To this, long-range oxygen ordering may go along with complex electronic ordering, as observed for the spin structure in the homologous Nd2NiO4.10 10 , yielding to interesting correlations. 14,22 Ordering phenomena and their interplay are generally difficult to explore related to weak satellite intensities and the availability of single phases. The availability of high purity single crystals, suitable for elastic and inelastic neutron scattering studies, are thus mandatory.…”

Large-scale oxygen order phase transitions and fast ordering kinetics at moderate temperatures in Nd2NiO4+δ electrodes

“…[1][2][3][4][5] In this regard, non-stoichiometric 214-nickelates (Ln 2 NiO 4+d ; Ln = La, Pr or Nd) of the Ruddlesden-Popper (RP) series with layered K 2 NiF 4 structure appear as one of the most promising candidates due to their electronic complexity and enhanced oxygen mobility down to ambient temperature. [5][6][7][8][9][10][11][12][13][14][15] The crystal structure of these compounds, as shown in Fig. 1(a), can be described as a layered structure with alternate stacking of NiO 2 layers and rock salt type Ln 2 O 2 bilayers along the stacking-axis (c-axis) of the tetragonal unit cell.…”

“…With increasing oxygen uptake the local distortions of the O int (O ap ) 4 tetrahedra get organized on a larger length scale, as evidenced by neutron and synchrotron diffraction experiments. 7,19,[28][29][30][31] Ordering schemes of unprecedent structural complexity have been reported for the homologous Pr 2 NiO 4+d , where sub-mesoscopic ordering is observed for d = 0.25 attaining translational periodicities of ca. 100 Å.…”