The Jahn-Teller effect of layered perovskite manganites La2−2xSr1+2xMn2O7 studied by Mn K-edge XAFS

In situ X-ray absorption spectroscopic study for the electrochemical delithiation of a cathode LiFe0.4Mn0.6PO4 material

“…Similar MnO 6 distortion with 2 and 4 oxygen atoms located at 0.183 and 0.212 nm has been observed for the NiO 6 octahedron in LiNiO 2 (Ni 3+ is Jahn-Teller active ion) [39]. The octahedron distortion with 4 and 2 atoms at short and long distances, respectively, has been reported for MnO 6 in perovskite manganites Ln 2−2x Sr 1+2x Mn 2 O 7 [40] and for NiO 6 in quasi-2D LiNiO 2 [41]. The calculated distortion parameters for bond lengths, d , according to a formula presented in Yamada PO 4 structure.…”

Electron correlations—the origin of the CE phase in bilayer La2−2xSr1+2xMn2O7manganites

“…We studied the ground states of 4 × 4 × 2 clusters in bilayer geometry (containing N = 32 sites) with periodic boundary conditions along crystallographic a and b axes, and free boundary conditions along the crystallographic c axis, assuming different hole concentration x = 1 − n (away from half-filling n = 1, where n is e g electron density), changing from x = 0.3 up to x = 0.88-all these dopings are well covered by the experimental data [17][18][19][20][21][22][23][24]. (Larger clusters such as 8 × 8 × 2 are feasible only for isolated computations but certainly not for computations involving the thousands of different initial conditions which were necessary in the present case in order to catch the multitude of closely spaced metastable ground states in a non-homogeneous system such as the bilayer manganite.)…”

“…Indeed, while an isotropic ferromagnetic (FM) phase in doped perovskite systems [15] is described by the orbital liquid [16], this class of compounds provides one of the best examples of the complexity of manganite physics. Their experimental properties, in particular information about the type of magnetic order and phase diagram (versus doping), were described in detail in a series of papers [17][18][19][20][21][22][23][24]. We present the effective model which, in our opinion, is a necessary compromise between simplicity and the requirement to include all basic and relevant factors responsible for the physical properties of bilayer La 2−2x Sr 1+2x Mn 2 O 7 compounds.…”

Pressure induced phase separation in optimally doped bilayer manganites

“…The lattice parameters of the sample at P = 0 are 3.8578͑1͒ and 20.1808͑7͒, in perfect agreement with previous reports. 7 The application of the external pressure causes an anisotropic contraction of the in-plane and out-of-plane crystal axes with a more pronounced shrinkage of the a-b tetragonal parameters, leading in turn to an increase in the tetragonal distortion parameter c / a ͑Fig. 1͒.…”