Mössbauer Studies of the High-Spin-Low-Spin Equilibria and the Localized-Collective Electron Transition in LaCo<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Bhide, V. G.; Rajoria, D. S.; Rao, G. Rama; Rao, C. N. R.

doi:10.1103/physrevb.6.1021

Cited by 328 publications

(137 citation statements)

References 35 publications

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“…From Laue photographs of both ends of the crystals we have found that LaCoO 3 and EuCoO 3 are single crystals, whereas the samples with 0 < x < 1 are polycrystalline. The electrical resistivity has been measured by a standard four-probe technique on bar-shaped samples of typical dimensions of 2 × 3 × 5 mm 3 . Wires have been attached by conductive silver epoxy to four gold stripes, which have been evaporated on the sample surface.…”

Section: Methodsmentioning

confidence: 99%

“…The magnetic susceptibility χ shows a maximum around 100 K that is usually ascribed to a spin-state transition from a nonmagnetic insulating state at low temperatures to a paramagnetic insulating state at higher temperatures. 2,3,4,5,6,7,8,9,10,11 In addition, around 500 K a metal-insulator transition occurs, 12,13 which is accompanied by an increase of the magnetic moment leading to a broad plateau in the magnetic susceptibility.…”

Section: Introductionmentioning

confidence: 99%

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Spin-state transition and metal-insulator transition inLa1−xEuxCoO3

et al. 2005

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We present a study of the structure, the electric resistivity, the magnetic susceptibility, and the thermal expansion of La1−xEuxCoO3. LaCoO3 shows a temperature-induced spin-state transition around 100 K and a metal-insulator transition around 500 K. Partial substitution of La 3+ by the smaller Eu 3+ causes chemical pressure and leads to a drastic increase of the spin gap from about 190 K in LaCoO3 to about 2000 K in EuCoO3, so that the spin-state transition is shifted to much higher temperatures. A combined analysis of thermal expansion and susceptibility gives evidence that the spin-state transition has to be attributed to a population of an intermediate-spin state without orbital degeneracy for x < 0.5 and with orbital degeneracy for larger x. In contrast to the spin-state transition, the metal-insulator transition is shifted only moderately to higher temperatures with increasing Eu content, showing that the metal-insulator transition occurs independently from the spin-state distribution of the Co 3+ ions. Around the metal-insulator transition the magnetic susceptibility shows a similar increase for all x and approaches a doping-independent value around 1000 K indicating that well above the metal-insulator transition the same spin state is approached for all x.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spin-state transition and metal-insulator transition inLa1−xEuxCoO3

et al. 2005

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“…The oxygen octahedra coordinating the cobalt ion in the prototypical perovskite structure controls the delicate balance between the Hund's coupling and the crystal field splitting energy for the d electrons of Co 3? [12]. At low temperatures (below *100 K), the latter dominates with Co 3?…”

Section: Introductionmentioning

confidence: 99%

Influence of Al doping in LaCoO3 on structural, electrical and magnetic properties

et al. 2014

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We report investigations on polycrystalline LaCo 1-x Al x O 3 (x = 0-0.9) bulk samples. The solid state synthesized samples showed a coexistence of rhombohedral and monoclinic phases in the intermediate concentrations (0.2 B x B 0.5) and pure rhombohedral phase otherwise. The observed effect of Al doping on dc transport has been analysed on the basis of small polaron hopping mechanism. The magnetisation results presented give evidence of weak ferromagnetism and anomalous temperature dependence of coercivity which we associate to the canting of the localised high-spin Co(III) and anti-symmetric exchange interactions at low temperatures.

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“…This directly shows that the currently accepted low-/intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance and inelastic neutron data.PACS numbers: 71.28.+d, 71.70.Ch, 78.70.Dm LaCoO 3 shows a gradual non-magnetic to magnetic transition with temperature, which has been interpreted originally four decades ago as a gradual population of high spin (HS, t 4 2g e 2 g , S = 2) excited states starting from a low spin (LS, t 6 2g , S = 0) ground state [1,2,3,4,5,6,7,8]. This interpretation continued to be the starting point for experiments carried out up to roughly the first half of the 1990's [9,10,11,12].…”

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confidence: 99%

Spin State Transition inLaCoO3Studied Using Soft X-ray Absorption Spectroscopy and Magnetic Circular Dichroism

et al. 2006

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Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L2,3 edge we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply-degenerate high-spin first excited state. From the temperature dependence of the spectral lineshapes we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spinstate system. Crucial is that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low-/intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance and inelastic neutron data.PACS numbers: 71.28.+d, 71.70.Ch, 78.70.Dm LaCoO 3 shows a gradual non-magnetic to magnetic transition with temperature, which has been interpreted originally four decades ago as a gradual population of high spin (HS, t 4 2g e 2 g , S = 2) excited states starting from a low spin (LS, t 6 2g , S = 0) ground state [1,2,3,4,5,6,7,8]. This interpretation continued to be the starting point for experiments carried out up to roughly the first half of the 1990's [9,10,11,12]. All this changed with the theoretical work in 1996 by Korotin et al., who proposed on the basis of local density approximation + Hubbard U (LDA+U) band structure calculations, that the excited states are of the intermediate spin (IS, t 5 2g e 1 g , S = 1) type [13]. Since then many more studies have been carried out on LaCoO 3 with the majority of them [14,15,16,17,18,19,20,21,22,23,24,25,26,27] claiming to have proven the presence of this IS mechanism. In fact, this LDA+U work is so influential [28] that it forms the basis of most explanations for the fascinating properties of the recently synthesized layered cobaltate materials, which show giant magneto resistance as well as metal-insulator and ferroferri-antiferro-magnetic transitions with various forms of charge, orbital and spin ordering [29,30].In this paper we critically re-examine the spin state issue in LaCoO 3 . There has been several attempts made since 1996 in order to revive the LS-HS scenario [31,32,33,34,35], but these were overwhelmed by the above mentioned flurry of studies claiming the IS mechanism [14,15,16,17,18,19,20,21,22,23,24,25,26,27]. Moreover, a new investigation using inelastic neutron scattering (INS) has recently appeared in Phys. Rev. Lett.[36] making again the claim that the spin state transition involves the IS states. Here we used soft xray absorption spectroscopy (XAS) and magnetic circular dichroism (MCD) at the Co-L 2,3 edge and we revealed that the spin state transition in LaCoO 3 can be well described by a LS ground state and a triply degenerate HS excited state, and that an inhomogeneous mixed-spinstate system is formed. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility and electron spin resonance (ESR) data, and provide support for an alternative interpretation of the INS [37]. C...

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Mössbauer Studies of the High-Spin-Low-Spin Equilibria and the Localized-Collective Electron Transition in LaCoO3

Cited by 328 publications

References 35 publications

Spin-state transition and metal-insulator transition inLa1−xEuxCoO3

Spin-state transition and metal-insulator transition inLa1−xEuxCoO3

Influence of Al doping in LaCoO3 on structural, electrical and magnetic properties

Spin State Transition inLaCoO3Studied Using Soft X-ray Absorption Spectroscopy and Magnetic Circular Dichroism

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