Ferromagnetism vs Paramagnetism and False Quantum Oscillations in Lanthanum-Doped CaB<sub>6</sub>

Terashima, Taichi; Terakura, C.; Umeda, Yuji; Kimura, Noriaki; Aoki, Haruyoshi; Kunii, S.

doi:10.1143/jpsj.69.2423

Cited by 48 publications

(49 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The necessary condition of a localized, non-constant La-DOS near E F , appears to be enforced as the doping decreases, and the mechanism of charge transfers persists at lower doping levels. Thus, it is likely that the observed weak ferromagnetism for dilute La-doping in hexaborides 4,5 , is a band effect of the kind that we have described. This conclusion is based on results from first-principle LMTO calculations.…”

Section: Discussionmentioning

confidence: 73%

“…Recent experimental works on La-doped hexaborides like La x Ca (1−x) B 6 show unexpectedly a very weak ferromagnetic state that persists up to large temperatures, and for very low x, about 0.005 4 . Independent measurements confirm these findings in part, but they also show that the results can span from weak ferromagnetism to strong paramagnetism and that Al impurities may conceal some of the intrinsic properties 5 . Ferromagnetism in the La-doped hexaborides XB 6 , X=Ca,Sr or Ba, is surprising because the density-ofstates (DOS) at the Fermi energy, N (E F ), and the Stoner factor,S, are expected to be small in this family of compounds.…”

Section: Introductionmentioning

confidence: 58%

“…The resulting DOS from In doping is very similar to the one from Al (or even B) doping, at least as long as lattice relaxation can be ignored. It has been reported that Al can penetrate the hexaboride material when the aluminum flux-growth technique is used to prepare single crystals 5 . The calculated results for single In or Al impurities shown here, indicate that the effects of Al contamination should be very different from those of La impurities.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, one must emphasize that the calculations show the likelihood of a ferromagnetic state, but that one can not be affirmative for the absolute values. This situation may reflect the reality, since different samples are reported to have different moments (at most 0.32 µ B /La), while some show only large paramagnetic susceptibilities 5 . Real materials have some randomness in the distribution of the impurities, while the calculations are made for ordered supercells.…”

Section: Discussionmentioning

confidence: 97%

See 3 more Smart Citations

Electronic structure and magnetism in slightly doped SrB6

Jarlborg

2001

Physica B: Condensed Matter

View full text Add to dashboard Cite

Spin-polarized band calculations for supercells of SrB6, where a La-, In-or Al-impurity or a vacancy is replacing one Sr, are performed within the local spin density approximation. Moderately large cells with 8 formula units (56 atoms) are studied for all dopings and large ones with 27 formula units (189 atoms) for the case of La-doping. The undoped system has a vanishing density-of-states (DOS) at the Fermi energy (EF ), while the additional La-d band makes EF to enter the bands above the gap. An Al (or In) impurity has the opposite effect, with a rigid-band like shift of EF to below the gap. In the former case, the addition of a d-electron makes a local, impurity-like modification of the electronic structure close to the La atom. As has been shown in a previous publication [Phys. Rev. Lett. 85, 186, (2000)], it can lead to a weak ferromagnetic state. This result is shown to persist at even lower doping, by the 189-atom cell calculations, with a moment of the order 0.1 µB per La impurity. An addition of a p-electron, by an In-impurity, makes no similar effect. The DOS at EF and the Stoner factors are in all cases low, and would not suggest ferromagnetism alone. The magnetic state can be understood from a charge transfer and an additional gain in potential energy, as a spin-splitting is imposed. A DOS with a localized impurity band is essential for this effect. Different models with modified localization of the La-band are made in order to show the correlation between charge transfer and the size of the magnetic moment.

show abstract

Section: Discussionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 97%

See 2 more Smart Citations

Electronic structure and magnetism in slightly doped SrB6

Jarlborg

2001

Physica B: Condensed Matter

View full text Add to dashboard Cite

show abstract

“…They argue that self-doping attributed to defects might occur. Terashima et al [19] reported strongly sample dependent data for Ca 0.995 La 0.005 B 6 and, lately, doubts about the intrinsic nature of the WF in these systems were raised [20]. It has been argued that CaB 6 is a ~1 eV-gap semiconductor and that the intrinsic WF could be hidden by the FM of Fe and Ni impurities at the surface of the crystals [21].…”

Section: Originalmentioning

confidence: 99%

Gd³⁺ and Eu²⁺ local environment in Ca_1–xEu_xB₆ (0.0001 ≤ x ≤ 0.30) and Ca_1–xGd_xB₆ (0.0001 ≤ x ≤ 0.01)

Urbano

Pagliuso

Rettori

et al. 2006

Physica Status Solidi (a)

View full text Add to dashboard Cite

TitleGd3+ and Eu2+ local environment in Ca1-xEuxB6 (0.0001 <= x <= 0.30) and Ca1-xGdxB6 (0.0001 <= x <= 0.01) 7 ions, S = 7/2, in Ca 1-x Eu x B 6 (0.0001 ≤ x ≤ 0.30) and Ca x Gd x B 6 (0.0001 ≤ x ≤ 0.01) is investigated by means of electron spin resonance (ESR). For x ≤ 0.001 the spectra show resolved fine structures due to the cubic crystal electric field and, in the case of Eu, the hyperfine structure due to the nuclear hyperfine field is also observed. The resonances have Lorentzian line shape, indicating insulating host for the Gd 3+ and Eu 2+ ions. As x increases, the ESR lines broaden due to local distortions caused by the Ca/Gd,Eu ions substitution. For Gd (x ≈ 0.001) and Eu (x ≈ 0.02), the spectra present superposition of Lorentzian and Dysonian resonances, suggesting a coexistence of insulating and metallic hosts for the Gd 3+ and Eu 2+ ions. The Gd 3+ and Eu 2+ fine structures are still observable up to x ≈ 0.003 for Gd and x ≈ 0.15 for Eu. For larger values of x the fine and hyperfine structures are no longer observed, the line width increases, and the line shape becomes pure Dysonian anticipating the metallic and semimetallic character of GdB 6 and EuB 6 , respectively. These results clearly show that in the low concentration regime the Ca 1-x R x B 6 (R = Gd, Eu) systems are intrinsically inhomogeneous. No evidence of weak ferromagnetism (WF) was found in the ESR spectra of either metallic or insulating phases of these compounds, suggesting that, if WF is present in these materials, the Gd 3+ and Eu 2+ 4f 7 -electrons are shielded from the WF field.

show abstract

The Electronic Properties of Cation‐Deficient K _1—x B ₆ and the New Cubic Carbaboride KB ₅ C

Okatov

Ivanovskiĭ

2000

phys. stat. sol. (b)

View full text Add to dashboard Cite

Introduction Considerable theoretical and experimental efforts [1,2] are devoted to metal the hexaborides (MB 6 , where M is rare-earth, alkaline and alkaline-earth metals) due to their interesting physical properties. Doping of the cation sublattice of MB 6 with metal atoms of a different type M H is a well-known method of modification of their properties. A large class of ternary hexaborides M 1Àx M H x B 6 has been obtained recently, for example, the rare-earth-metal-doped CaB 6 : Ca 1Àx La x B 6 , Ca 1Àx Eu x B 6 etc. [3,4]. The first ternary hexaborides containing substitutional impurities (C atoms) in the anion sublattice ± the so-called carbaborides NaB 5 C, KB 5 C ± have been synthesized recently [5]. Besides impurities, some hexaborides (for example, KB 6 , BaB 6 etc.) may contain structural defects of a different type, such as cationic vacancies [1]. In this communication we report the first theoretical findings concerning the electronic properties of cation-deficient potassium hexaborides K 1Àx B 6 and the new ternary phase ± carbaboride KB 5 C.Computational The cubic hexaboride KB 6 (space group O 1

show abstract

Ferromagnetism vs Paramagnetism and False Quantum Oscillations in Lanthanum-Doped CaB₆

Cited by 48 publications

References 15 publications

Electronic structure and magnetism in slightly doped SrB6

Electronic structure and magnetism in slightly doped SrB6

Gd³⁺ and Eu²⁺ local environment in Ca_1–xEu_xB₆ (0.0001 ≤ x ≤ 0.30) and Ca_1–xGd_xB₆ (0.0001 ≤ x ≤ 0.01)

The Electronic Properties of Cation‐Deficient K _1—x B ₆ and the New Cubic Carbaboride KB ₅ C

Contact Info

Product

Resources

About

Ferromagnetism vs Paramagnetism and False Quantum Oscillations in Lanthanum-Doped CaB6

Cited by 48 publications

References 15 publications

Electronic structure and magnetism in slightly doped SrB6

Electronic structure and magnetism in slightly doped SrB6

Gd3+ and Eu2+ local environment in Ca1–xEuxB6 (0.0001 ≤ x ≤ 0.30) and Ca1–xGdxB6 (0.0001 ≤ x ≤ 0.01)

The Electronic Properties of Cation‐Deficient K 1—x B 6 and the New Cubic Carbaboride KB 5 C

Contact Info

Product

Resources

About

Ferromagnetism vs Paramagnetism and False Quantum Oscillations in Lanthanum-Doped CaB₆

Gd³⁺ and Eu²⁺ local environment in Ca_1–xEu_xB₆ (0.0001 ≤ x ≤ 0.30) and Ca_1–xGd_xB₆ (0.0001 ≤ x ≤ 0.01)

The Electronic Properties of Cation‐Deficient K _1—x B ₆ and the New Cubic Carbaboride KB ₅ C