Oxygen deficiency in Sr2FeO4−x: electrochemical control and impact on magnetic properties

Adler, Peter; Schröder, Liane; Teske, K.; Reehuis, M.; Hoser, A.; Merz, Patrick; Schnelle, Walter; Felser, Claudia; Jansen, Martin

doi:10.1039/d2cp02156k

Cited by 4 publications

(4 citation statements)

References 57 publications

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“…Lattice parameters and are better reproduced by WC3PW and PBE1PBE, respectively. In addition, the WC3PW functional gives a very good result for the ratio / =3.20 vs 3.22 41 , 3.21 25 . Both functionals, WC3PW and PBE1PBE, suggest comparable results for the equilibrium volume as it is by 2 Å smaller for WC3PW but larger for PBE1PBE compared to the experimental value.…”

Section: Methodsmentioning

confidence: 90%

“…It is essential that both these experiments (Refs. 25 , 41 ), also containing low-temperature data, show weak SFO structure parameter dependence on temperature over a wide interval. Thus, the low-temperature experimental structure parameters may be directly compared with the first-principles calculations results at 0 K.…”

Section: Methodsmentioning

confidence: 97%

“…Notice that the formal value for in the high spin state ( ) is 4. In recent magnetic experiments 15 , 41 , it is established that SFO adopts a cycloidal elliptical spin spiral magnetic structure below with magnetic moments modulation from 1.9 to 3.5 . We consider the present hybrid DFT calculated values of to be quite consistent with the experimental values, taking into account our simplified model for magnetism.…”

Section: Methodsmentioning

confidence: 99%

“…Following our approach described above, we consider SFO in two main different SG models taken as one basic I 4/ mmm (so far the only one suggested in the literature for SFO) and one new Cmce model (suggested in the presented study). The tetragonal I 4/ mmm ( tI , , SG 139) model is considered to index experimentally obtained SFO structure from the ambient temperature down to 4 K in 25 and 1.8 K in 41 . Here the primitive ( tP ) and body-centered ( tI ) tetragonal crystallographic bases are connected with a transformation matrix The ion Wyckoff positions (WP) and corresponding point symmetries in the crystallographic cell are given in Table 1 .…”

Section: Group-theoretical Analysismentioning

confidence: 99%

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Jahn–Teller distortion in Sr2FeO4: group-theoretical analysis and hybrid DFT calculations

Zvejnieks,

Mastrikov,

Gryaznov

2023

Sci Rep

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We present theoretical justification for distorted Ruddlesden–Popper (RP) phases of the first-order by using hybrid density functional theory (DFT) calculations and group-theoretical analysis. We, thus, demonstrate the existence of the Jahn–Teller effect around an Fe$$^{4\texttt {+}}$$ 4 + ion in Sr$$_{2}$$ 2 FeO$$_{4}$$ 4 . On the calculation side, we have established a combination of Wu–Cohen (WC) exchange and Perdew-Wang (PW) correlation in a three-parameter functional WC3PW, giving the most accurate description of Sr$$_{2}$$ 2 FeO$$_{4}$$ 4 from the comparison of three hybrid DFT functionals. Self-consistently obtained Hartree–Fock exact exchange of 0.16 demonstrates consistent results with the experimental literature data. Importantly, we explain conditions for co-existing proper and pseudo-Jahn–Teller effects from the crystalline orbitals, symmetry-mode analysis and irreps products. Moreover, phonon frequency calculations support and confirm the results of symmetry-mode analysis. In particular, the symmetry-mode analysis identifies a dominating irreducible representation of the Jahn-Teller mode (X2) and corresponding space group (SG) of ground state structure (SG Cmce model). Therefore, the usually suggested high-symmetry tetragonal crystal structure (SG I4/mmm model) is higher in energy by 121 meV/f.u. (equivalent to the Jahn-Teller stabilization energy) compared with the distorted low-symmetry structure (SG Cmce model). We also present diffraction patterns for the two crystal symmetries to discuss the differences. Therefore, our results shed light on the existence of low-symmetry RP phases and make possible direct comparisons with future experiments.

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