Use of the Jahn-Teller theorem in inorganic chemistry

Burdett, Jeremy K.

doi:10.1021/ic50221a003

Cited by 90 publications

(89 citation statements)

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“…Thus, the e 9 -mixing cannot play an important role. 4. s-d-mixing: 4s-3d22-mixing is assumed to explain the favouring of the elongation of MX 6 -octahedra in strong Jahn-Teller systems (£ g ground state) [59,60]. Its importance in our Mn(III) systems is documented in the large local anisotropy (about 3 K) connected with such a process.…”

Section: Possible Exchange Pathwaysmentioning

confidence: 99%

Magnetism of Alkalitetrafluoromanganates (III) AMnF₄ (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Molinier

Frommen

Massa

et al. 1993

Zeitschrift Für Naturforschung A

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The magnetic properties of the d 4 Jahn-Teller systems A'Mn m F 4 with layered structures were investigated. Neutron diffraction on powders of KMnF 4 and RbMnF 4 revealed different antiferromagnetic spin arrangements below T N = 4.5 K and 2.3 K, respectively: for KMnF 4 canted antiparallel along a and b, for RbMnF 4 parallel along a and antiparallel along b, in both cases parallel along c, the stacking direction of layers. Mössbauer investigations on 57 Fe doped KMnF 4 confirmed a spin orientation approximately within the layer plane. A discussion is given of the contributions to the magnetic hyperfine field and the Mössbauer linewidth in quasi-two-dimensional antiferromagnets with Ising anisotropy due to thermal excitation of domain wall dynamics (solitons). The experimental data seem to confirm the predicted exponential temperature dependence of the linewidth. From magnetization measurements on powders and a single crystal of KMnF 4 the 2-d exchange energy and the out-of-plane and in-plane anisotropies could be extracted. In addition, from susceptibility measurements the exchange energies of NaMnF 4 , RbMnF 4 and CsMnF 4 were calculated. A linear dependence of these exchange energies (positive for ferromagnetic CsMnF 4 , negative for the other AMnF 4 compounds) on the cos 2 of the Mn-F-Mn bridge angle is observed and compared with the behaviour of the AFeF 4 compounds which is also linear but with reverse sign of the slope. The specific superexchange mechanisms active in Jahn-Teller systems with antiferrodistortively ordered layers are suggested to be responsible for these findings.

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Section: Possible Exchange Pathwaysmentioning

confidence: 99%

Magnetism of Alkalitetrafluoromanganates (III) AMnF₄ (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Molinier

Frommen

Massa

et al. 1993

Zeitschrift Für Naturforschung A

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“…The large polarization is due to the large atomic displacements induced by the sulfur replacement. Figure. 6 as a function of the magnitude of the P mode with a fixed Q mode (Q = 1). For simplicity, we adopt the fractional unit for the P and Q modes, i.e., we rescale the P and Q to the dimensionless quantities: P = 1 and Q = 1 mean that the total displacements of P and Q modes are equal to 0.0496 and 0.8218 Å respect to the 20-atom R32=m La 2 (Co,Al)O 6 PE structure.…”

Section: General Design Guidelinesmentioning

confidence: 99%

“…5 For traditional proper FEs, such as BaTiO 3 , the transition metal ion Ti 4+ with d 0 configuration can hybridize with the oxygen 2p states leading to the FE phase transition due to the pseudo Jahn-Teller effect. [6][7][8][9][10] However, FEs are very few in nature. 11 To find more high-performance FEs, improper (including hybrid improper) FEs become an intense research field.…”

Section: Introductionmentioning

confidence: 99%

Designing new ferroelectrics with a general strategy

Xiang

2017

npj Quant Mater

104

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The presence of a switchable spontaneous electric polarization makes ferroelectrics ideal candidates for the use in many applications such as memory and sensors devices. Since known ferroelectrics are rather limited, finding new ferroelectric materials has become a flourishing field. One promising route is to design the improper ferroelectrics. However, previous approach based on the Landau theory is not easily adopted for systems that are unrelated to the Pbnm perovskite structure. To this end, we develop a general design rule that is applicable to any system. By combining this rule with the density functional theory calculations, we identify previously unrecognized classes of ferroelectric materials. It is shown that the R3c perovskite structure can become ferroelectric by substituting half of the B-site cations. Compound ZnSrO 2 with a non-perovskite layered structure can also be ferroelectric through the anion substitution. Moreover, our approach can be used to design new multiferroics as illustrated in the case of fluorine substituted LaMnO 3 . 13 where the FE buckling (P mode) of the Y-O planes is induced by the non-polar MnO 5 polyhedra tilt (Q mode). 13,14 The free energy expansion in this system contains the coupling term (PQ 3 ) between the Q and P, indicating that the non-polar distortion Q must be reversed. 15 The hybrid improper ferroelectricity (HIF) was recently discovered in the artificial superlattice PbTiO 3 /SrTiO 3 , 16 where the ferroelectricity is induced by a trilinear coupling (PQ 1 Q 2 ) between the FE mode (P) and two oxygen octahedral rotational modes (Q 1 and Q 2 , respectively). The HIF was also found in the double-layered Ruddlesden-Popper (RP) perovskite A 3 B 2 O 7 (A=Ca, Sr; B=Mn,Ti), 17-19 the 1:1 A-cation ordering perovskite-type superlattice, 20-23 A-cation ordering RP NaRTiO 4 (R = Y, La, Nd, Sm-Ho), 24 the 2:2 B-cation ordered superlattice, 25 and metal-organic perovskite material. 26 In the above-mentioned theoretically designed FEs, one usually starts from a high-symmetry structure (e.g., cubic perovskite structure), then the effect of atomic substitution and soft phonon modulations are examined to see whether the ferroelectricity can be induced or not. Finally, the trilinear coupling mechanism is discussed to understand the origin of improper ferroelectricity. This procedure is indeed informative. However, it is tedious and its applicability to other type of compounds is limited since even the

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“…The structural non-rigidity of CuZ+X6 chromophores in the solid state has been recognized long ago. The observed tetragonal distortions originate from the JahnTeller effect (Burdett, 1981;Huheey, 1983b;Orpen et al, 1989;Burton & Deeth, 1995). Still, in the past, Hathaway (1973) has tried to explain the tetragonality in terms of the 'asymmetry' of the effective radius of the Cu 2+ ion; he has argued that in a regular octahedron, Cu z+ is spherically symmetric, but in an elongated octahedron it becomes prolate ellipsoid.…”

Section: Impficationsmentioning

confidence: 99%

New Bond-Valence Sum Model

Naskar¹,

Hati²,

Datta³

1997

Acta Crystallogr B Struct Sci

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A new expression is devised empirically to accommodate zero and some negative oxidation states in the bondvalence sum approach. The method is worked out in detail for a number of homoleptic copper and nickel complexes of various coordinating atoms in several oxidation states of the metals. An implication of the expression is a linear variation between 1/req and 1/rax in octahedral MX 6 moieties, where req and tax are, respectively, the average equatorial and axial bond lengths. This is verified in Cu2+X6 chromophores for X=F, O, N and S. The usefulness of the new expression in assessing the compatibility of a coordination sphere with an oxidation state of a metal ion is demonstrated by exemplary applications to some inorganic complexes, azurin and urease. references therein; Donnay & Donnay, 1973; Brown, 1978, and references therein; O'Keeffe, 1989, and references therein; Brown, 1992, and references therein;.It has been realized from the beginning that v o. bears an inverse relation with the distance (r) between two atoms i and j -a shorter bond implies higher v,j, while a longer bond indicates lower vo.. However, the exact relation between vv and r o.is not yet known. Several empirical forms have been suggested over the years (Donnay &

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Use of the Jahn-Teller theorem in inorganic chemistry

Cited by 90 publications

References 0 publications

Magnetism of Alkalitetrafluoromanganates (III) AMnF₄ (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Magnetism of Alkalitetrafluoromanganates (III) AMnF₄ (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Designing new ferroelectrics with a general strategy

New Bond-Valence Sum Model

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Use of the Jahn-Teller theorem in inorganic chemistry

Cited by 90 publications

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Magnetism of Alkalitetrafluoromanganates (III) AMnF4 (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Magnetism of Alkalitetrafluoromanganates (III) AMnF4 (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Designing new ferroelectrics with a general strategy

New Bond-Valence Sum Model

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Product

Resources

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Magnetism of Alkalitetrafluoromanganates (III) AMnF₄ (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Magnetism of Alkalitetrafluoromanganates (III) AMnF₄ (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations