Band Theory for Ground-State Properties and Excitation Spectra of Perovskite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>La</mml:mi><mml:mi mathvariant="italic">M</mml:mi><mml:mrow><mml:msub><mml:mrow><mml:mi>O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">M</mml:mi><mml:mspace /><mml:mo>=</mml:mo><mml:mspace /></mml:math>M

Sarma, D. D.; Shanthi, N.; Barman, S. R.; Hamada, Nobuyuki; Sawada, Hideaki; Terakura, Kiyoyuki

doi:10.1103/physrevlett.75.1126

Cited by 276 publications

(132 citation statements)

References 23 publications

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“…Empirically one finds that LDA/GGA band gaps are invariably much smaller than those predicted by the UHF method and in the limit of the LDA implementation of DFT LaMnO 3 band gap is predicted to be ϳ0.2 eV, one order of magnitude smaller than the experimental value. 12,57 Within the SIC point of view the hybrid exchange functionals can be considered to be a crude form of a screened exchange approximation in which the bare diagonal exchange interaction of UHF theory is screened with the semilocally approximated exchange of the LDA and GGA. Certainly the introduction of Fock exchange in the exchange functional has a very large effect as has already been pointed out by several authors.…”

Section: Electronic Structurementioning

confidence: 99%

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

2004

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The electronic and magnetic structures of the LaMnO 3 compound have been studied by means of periodic calculations within the framework of spin polarized hybrid density-functional theory. In order to quantify the role of approximations to electronic exchange and correlation three different hybrid functionals have been used which mix nonlocal Fock and local Dirac-Slater exchange. Periodic Hartree-Fock results are also reported for comparative purposes. The A-antiferromagnetic ground state is properly predicted by all methods including Hartree-Fock exchange. In general, the different hybrid methods provide a rather accurate description of the band gap and of the two magnetic coupling constants, strongly suggesting that the corresponding description of the electronic structure is also accurate. An important conclusion emerging from this study is that the nature of the occupied states near the Fermi level is intermediate between the Hartree-Fock and local density approximation descriptions with a comparable participation of both Mn and O states.

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Section: Electronic Structurementioning

confidence: 99%

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

2004

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“…< < . , are closely related and mainly interpreted in terms of a double-exchange (DE) mechanism [35 -37] including polaronic effects [38] [39,40]. Above c T , the g e electrons are localized by a random spin -dependent potential and conduction is by variable-range hopping (VRH) [49, 41 -43] or a polaronic transport mechanism [44][45][46].…”

Section: Low-angle X-ray Reflectometry -Laxrrmentioning

confidence: 99%

Structure and transport properties of coherently strained La_2/3Ca_1/3MnO₃/SrTiO₃ superlattices

Klein

Herbstritt

et al. 2005

Physica Status Solidi (b)

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We have prepared high quality, coherently strained La 2/3 Ca 1/3 MnO 3 /SrTiO 3 superlattices with different modulation periods by laser molecular beam epitaxy on (001) SrTiO 3 and NdGaO 3 substrates. A detailed structural characterization was performed by high-angle X-ray diffraction (HAXRD) and low-angle X-ray reflectivity (LAXRR). All superlattices are very flat, show excellent structural coherence and very small mosaic spread (0.02°). The in-plane coherency strain was varied by changing the thickness ratio of the constituent layers allowing for a systematic variation of the resulting tetragonal distortion of LCMO. The c-axis lattice parameter of LCMO could be continuously changed from 3.87 Å to 3.79 Å. The interface roughness was analyzed by offset low-angle X-ray reflectivity and low-angle rocking curve measurements. It was found to be of the order of one unit cell with a significant part of the roughness being vertically correlated. The strain induced tetragonal distortion of LCMO was found to cause strong reduction of the paramagnetic to ferromagnetic transition temperature from about 260 to 120 K and an increase of resistivity. The transport properties in the paramagnetic regime could be well described by a small polaron hopping model. The lattice distortions were found to result in a significant increase of the polaron trapping energy. Our results show that coherently strain superlattices are an interesting model system for the systematic study of the effect of lattice distortions on the magnetic and electronic properties of the doped manganites.

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“…6 A spin-polarized * conduction band of mainly 3d(e g ↑) character 7 is supposed to be responsible for the ''metallic'' character of the current transport below T C . 8 The Mn 3ϩ ion has one e g electron, whereas the Mn 3ϩ ion has none. When the concentration of the divalent A-site cation ͑Ca, for example͒ is 0.3, the occupancy of the * band is 0.7, which corresponds to the strongest ferromagnetism and the greatest magnetoresistance.…”

mentioning

confidence: 99%

Magnetic localization in mixed-valence manganites

1997

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The metal-insulator transition is mixed-valence manganites of the ͑La 0.7 Ca 0.3 ͒MnO 3 type is ascribed to a modification of the spin-dependent potential J H s-S associated with the onset of magnetic order at T C . Here J H is the on-site Hund's-rule exchange coupling of an e g electron with sϭ1/2 to the t 2g ion core with S ϭ3/2. Above T C , the e g electrons are localized by the random spin-dependent potential and conduction is by variable-range hopping. Over the whole temperature range, the resistivity varies as ln( / ϱ ) ϭ͓T 0 ͕1Ϫ(M /M S ) 2 ͖/T͔ 1/4 , where M /M S is the reduced magnetization. The temperature and field dependence of the resistivity deduced from the molecular-field theory of the magnetization reproduces the experimental data over a wide range of temperature and field. ͓S0163-1829͑97͒04513-X͔ Interest in mixed-valence manganites of the ͑La 0.7 Ca 0.3 ͒MnO 3 type has revived 1 with the observations of large negative magnetoresistive effects, 2,3 especially in suitably annealed thin films. 4 The magnetoresistance is greatest in the vicinity of the Curie point T C of ferromagnetic compositions which exhibit ''metallic'' ͑temperature-independent͒ conduction at low temperatures and thermally activated conduction above T C . These compositions have a structure which is a variant of the cubic perovskite cell where the Mn-O bond lengths are unequal and Mn-O-Mn bond angles differ from 180°. 5 Their electronic properties are related to electron hopping among the Mn ions in octahedral sites; metallic conductivity and ferromagnetism are closely related and are generally interpreted in terms of the doubleexchange mechanism. 6 A spin-polarized * conduction band of mainly 3d(e g ↑) character 7 is supposed to be responsible for the ''metallic'' character of the current transport below T C . 8 The Mn 3ϩ ion has one e g electron, whereas the Mn 3ϩ ion has none. When the concentration of the divalent A-site cation ͑Ca, for example͒ is 0.3, the occupancy of the * band is 0.7, which corresponds to the strongest ferromagnetism and the greatest magnetoresistance. Electron transfer with spin memory is an essential ingredient for an understanding of the transport properties of mixed-valence manganites, but something more is needed to account for the metal-insulator transition near the Curie point. 9 The change of conduction regime below T C appears to be brought about by the onset of ferromagnetism. As temperature decreases, the magnetization increases and the resistivity drops. Resistivity has been reported to vary like ͓1Ϫ(M /M S ) 2 ͔, as in conventional giant magnetoresistance ͑GMR͒ systems, 10 but others find an exponential dependence 11 ln( )ϳϪM/M S . Here we propose the concept of magnetic localization to relate the resistivity at any temperature or applied field to the local magnetization, evaluated in the molecular field approximation. The model involves variable range hopping and goes beyond the purely phenomenological parallel conduction model of Nunez-Reiguero and Kadin. 12 We previously observed an impr...

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Band Theory for Ground-State Properties and Excitation Spectra of PerovskiteLaMO3(M=M

Cited by 276 publications

References 23 publications

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

Structure and transport properties of coherently strained La_2/3Ca_1/3MnO₃/SrTiO₃ superlattices

Magnetic localization in mixed-valence manganites

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Band Theory for Ground-State Properties and Excitation Spectra of PerovskiteLaMO3(M=M

Cited by 276 publications

References 23 publications

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

Structure and transport properties of coherently strained La2/3Ca1/3MnO3/SrTiO3 superlattices

Magnetic localization in mixed-valence manganites

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Structure and transport properties of coherently strained La_2/3Ca_1/3MnO₃/SrTiO₃ superlattices