Effect of magnesium doping on the orbital and magnetic order inLiNiO2

Abstract

In LiNiO2, the Ni 3+ ions, with S=1/2 and twofold orbital degeneracy, are arranged on a triangular lattice. Using muon spin relaxation (µSR) and electron spin resonance (ESR), we show that magnesium doping does not stabilize any magnetic or orbital order, despite the absence of interplane Ni 2+ . A disordered, slowly fluctuating state develops below 12 K. In addition, we find that magnons are excited on the time scale of the ESR experiment. At the same time, a g factor anisotropy is observed, in agreement with |3z 2 − r 2 orbital occupancy.

Magnetic phase diagram of theS= 1/2 triangular layered compound NaNiO2: a single crystal study

“…When Li is deintercalated, in Li z NiO 2 , short range incommensurate antiferromagnetic order is observed for z=3/4 and 2/3 [3]. As for the orbital part, several experimental works are in favor of the |3z 2 − r 2 orbital occupancy for the e g electrons with finite range order [4] or dynamical effects [2]. Such an occupancy is indeed observed unambiguously in the parent compound NaNiO 2 , which seems to behave more classically.…”

First-principles theory of doping in layered oxide electrode materials

“…[3][4][5] Doping LiMO 2 with transition-metal and non-transitionmetal impurities has been shown to be an effective way to optimize the electrochemical performance. [6][7][8][9][10][11][12][13][14][15][16][17][18][19] Here, the impurities (i.e., dopants) can be incorporated into LiMO 2 at the transition-metal (M) and/or Li sites and the lattice site preference of some of the dopants may be dependent on the experimental conditions during synthesis. Understanding the effects of doping requires a detailed understanding of the interaction between the dopant and the host, including intrinsic point defects that may present in the host compound, under the synthesis conditions.…”

Changes in the crystal and electronic structure of LiCoO2 and LiNiO2 upon Li intercalation and de-intercalation

“…From experimental investigations the magnetic ordering is still unclear, and there is some experimental evidence that long-range orbital ordering does not exist. 28 However, stoichiometric LiNiO 2 is non-existent, and the experimentally observed non-stoichiometry of LiNiO 2 may very well be a reason for this unsolved matter. 28 Although the simulation of XPS spectra by first principles calculations has been studied and compared to experiment for fully lithiated LiCoO 2 , 7,9 to our knowledge a detailed analysis of the DOS and PDOS and simulation of XPS spectra for changing lithium content x (0 o x r 1) in direct comparison with experiment for either system, Li x CoO 2 and Li x NiO 2 , has not been done yet.…”