Stabilization of the high-spin state of Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow/><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math>in LaCo<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>Rh<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/

Knı́žek, K.; Hejtmánek, J.; Maryško, M.; Jirák, Z.; Buršík, J.

doi:10.1103/physrevb.85.134401

Cited by 24 publications

(16 citation statements)

References 20 publications

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“…It results in more covalent bonding with its O neighbors which in turn weakens the covalent bonding between those and the next-neighbor Co atoms promoting the HS states on them. 40,41 Since the holes are mobile this picture should be viewed only as a simplified static analog of a complex dynamical equilibrium.…”

Section: 31mentioning

confidence: 99%

Doping Induced Spin State Transition inLaCoO3: Dynamical Mean-Field Study

2013

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The hole and electron doped LaCoO3 is studied using the dynamical mean-field theory. The oneparticle spectra are analyzed and compared to the available experimental data, in particular the x-ray absorption spectra. Analyzing the temporal spin-spin correlation functions we find the atomic intermediate spin state is not important for the observed Curie-Weiss susceptibility. Contrary to commonly held view about the roles played by the t2g and eg electrons we find narrow quasi-particle bands of t2g character crossing the Fermi level accompanied by strongly damped eg excitations.PACS numbers: 75.30. Wx,71.28.+d,75.20.Hr,71.10.Fd The electron-electron repulsion within the partially filled d shell is for a long time known to place the transition metal oxides among the most puzzling materials with properties varying substantially upon a small change of temperature, pressure, or carrier concentration. More recently the Hund's intra-atomic exchange and the competition between various spin states come to the spotlight as one of the key features in the physics of iron pnictides. 1,2However, the spin state competition is a much broader phenomenon 3 and we are only starting to understand its implications for the properties of materials.LaCoO 3 is a prototypical system with competing spin states. A small gap non-magnetic insulator at low temperature acquires Curie-Weiss (CW) susceptibility above 100 K 4 followed by disappearance of the charge gap between 450 and 600 K.5 The generally accepted explanation is essentially atomic physics of the low spin (t 6,7At < 18% Sr concentration microscopically inhomogeneous phase is observed that can be described as magnetic clusters separated by non-magnetic insulating matrix. Above 18% Sr concentrations the material becomes a homogeneous ferromagnetic (FM) metal. The interplay of spin state competition with the itinerant electron physics opens interesting possibilities 2 , which are yet to be investigated.Properties of La 1−x Sr x CoO 3 are commonly discussed in the context of double-exchange model which provides a satisfactory description of related La 1−x Sr x MnO 3 family. In this picture the t 2g electrons are localized on the metal atom forming the local spin moment while e g electrons form dispersive bands. Numerous comparative studies, however, found sizeable differences between cobaltites and manganites. Colossal magnetoresistance, the hallmark of manganite physics, is not found in cobaltites. 6,8The NMR relaxation rates in cobaltites are several orders of magnitude larger than in manganites.9 The linear specific heat coefficient in La 0.7 Sr 0.3 CoO 3 is 16 times larger than in La 0.7 Sr 0.3 MnO 3 .8 These observations raise the question of the relevance of the double-exchange picture for doped cobaltites.The strong T -dependence of physical properties even in the parent compound LaCoO 3 make theoretical description of cobaltites challenging. Several density functional and Hartree-Fock calculations on doped cobaltites were reported. [10][11][12][13][14] In this Letter we use ...

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Section: 31mentioning

confidence: 99%

Doping Induced Spin State Transition inLaCoO3: Dynamical Mean-Field Study

2013

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“…In case of LaCo 1−x Mn x O 3 , where LaMnO 3 is antiferromagnetic insulator and crystallizes in an orthorhombic structure, detailed magnetization and neutron diffraction studies arXiv:1801.04401v1 [cond-mat.str-el] 13 Jan 2018 suggest the ferromagnetic/glassy nature and structural transition with Mn concentration [47]. Another interesting case is the substitution of 4d elements like nonmagnetic Rh 3+ , which is isoelectronic to Co 3+ and therefore, no charge transfer is expected [51][52][53]. Also, the 4d orbitals are much more extended than 3d orbitals, which results in the decreasing the correlation.…”

Section: Introductionmentioning

confidence: 99%

Anomalous magnetic and spin glass behavior in Nb-substituted LaCo1−xNbxO3

Shukla

Dhaka

2018

Phys. Rev. B

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We report the structural, magnetic, transport and electronic properties of Nb substituted LaCo1−xNbxO3 (x = 0-0.2). The Rietveld analysis of x-ray diffraction data demonstrate structural phase transitions from rhombohedral to orthorhombic and further to monoclinic with increasing the Nb concentration up to x ≥ 0.2. Interestingly, we observed dramatic changes in the magnetization (M) with increasing the Nb concentration, as the M sharply increases below 10 K even at 2.5% substitution. Furthermore, ac susceptibility data show the spin-glass behavior in x = 0.1 sample. We find that the density of states near the Fermi level decreases and the activation energy increases, which results in the decreasing conductivity with higher Nb concentration. A significant shift in the peak position of A2g phonon mode has been observed using Raman spectroscopy, which indicates the change in the coupling due to the structural distortion with Nb substitution. The core-level photoemission study confirms that the Nb is present in 5+ valence state. Our study reveals that the nonmagnetic Nb 5+ (d 0 ) substitution converts Co 3+ ions to Co 2+ and stabilize both in the high-spin state. Our results suggest that structural and spin-state transitions as well as the difference in the ionic radii between Nb 5+ and Co 3+ are playing an important role in tuning the physical properties.

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“…Later, Kyomen et al [27] in the light of the results of Al and Ga substitution in LaSrCoO 4 by Demazeau et al [28] comprehended this stabilization as arising from the weaker covalency of Al-O bond and Ga-O bonds compared to Co-O bonds. A similar substitution of Rh on the other hand stabilizes the HS states of Co(III) [27,29]. Motivated by these results we have performed a systematic investigation of polycrystalline LaCo 1-x Al x O 3 (x = 0, 0.2, 0.3, 0.5, 0.8, 0.9) with special emphasis to the structural, morphological and dc transport mechanism.…”

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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Stabilization of the high-spin state of Co3+in LaCo1−xRh

Cited by 24 publications

References 20 publications

Doping Induced Spin State Transition inLaCoO3: Dynamical Mean-Field Study

Doping Induced Spin State Transition inLaCoO3: Dynamical Mean-Field Study

Anomalous magnetic and spin glass behavior in Nb-substituted LaCo1−xNbxO3

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

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