Erratum:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">K</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Cr</mml:mi><mml:mn>8</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>16</mml:mn></mml:msub></mml:mrow></mml:math>predicted as a half-metallic ferromagnet: Scenario for a metal-insulator transition [Phys. Rev. B<b>80</b>, 024416 (2009)]

Sakamaki, Masako; Konishi, Toshifumi; Ohta, Y.

doi:10.1103/physrevb.82.099903

Cited by 18 publications

(28 citation statements)

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“…The number of d electrons thus indicates that the second band counted from the top in the t 2g manifold crosses the Fermi level with the filling of electrons roughly between a half to three quarters if the second band is isolated (although of course more than one band can cross the Fermi level). Our preliminary electronic structure calculations indicate that the band structure is not very simple but there is in fact a highly quasi-one-dimensional band, as expected from our results for K 2 Ru 8 O 16 , which is consistent with the quasi-one-dimensional transport properties reported in Ba [3] have shown that the system is a fully spin-polarized half metal and that the Fermi level is located between the third and fourth bands counted from the top of the t 2g manifold for majority-spin electrons, or that both of the third and fourth bands cross the Fermi level to form a semimetallic (or compensated metallic) band structure.…”

Section: Introductionsupporting

confidence: 79%

“…We thereby examine the 3d series (M =Ti, V, Cr, Mn) as well as the 4d series (M =Mo, Ru, Rh) to discuss generic features in the electronic structure of hollandites first. Then, we in particular study the quasi-one-dimensional electron conduction observed in K [2,3] is discussed in this respect. We also study the electronic structure of K 2 V 8 O 16 to consider the origins of the observed anomalous electronic states and metal-insulator transition [4].…”

Section: Introductionmentioning

confidence: 99%

“…These states come predominantly from the Cr 3d d yz and d zx orbitals with strong admixture of the O(2) 2p z orbitals between the double chains. The negative charge-transfer-gap situation [3] plays an essential role here. The calculated Fermi surfaces are shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Anomalous electronic states of hollandite-type transition-metal oxides

Ohta

Toriyama

Sakamaki

et al. 2012

J. Phys.: Conf. Ser.

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Abstract. We make the electronic structure calculations of transition-metal oxides with the hollandite-type crystal structure A2M8O16 using the generalized gradient approximation (GGA) in the density functional theory, where the Hubbard-type repulsive interaction is taken into account (GGA+U ). We first discuss generic electronic structures of the 3d (M =Ti, V, Cr, Mn) and 4d (M =Mo, Ru, Rh) series of the materials and then consider the origins of the metal-insulator transition observed in K2Cr8O16 and quasi-one-dimensional electron conduction observed in K2Ru8O16. We also consider in particular the observed metal-insulator transition in K2V8O16. IntroductionHollandite materials have attracted considerable attention in recent years in the field of physics of strong electron correlations. The crystal structure of hollandites resembles that of the rutile structure but the single chains of M O 6 octahedra (M =transition element) in rutiles are replaced by the double chains of the edge-shared M O 6 octahedra in hollandites, resulting in a sparse structure with large tunnels, wherein a variety of cations A can be introduced as in the chemical formula A x M 8 O 16 with 0 ≤ x ≤ 2. We point out that the material series with the 3d transitionmetal elements M = Ti, V, Cr, and Mn, which are in a mixed valent state, show a variety of unusual electronic and magnetic properties, including the metal-insulator transition, spinsinglet formation, as well as ferromagnetism and antiferromagnetism. The material series with the 4d transition-metal elements M = Mo, Ru, and Rh also show interesting physical properties, including the quasi-one-dimensional electron conduction [1].In this paper, motivated by such materials development, we make the electronic structure calculations on the series of hollandite-type transition-metal oxides to clarify their basic electronic structures. We use the generalized gradient approximation (GGA) in the density functional theory, where the Hubbard-type repulsive interaction U is taken into account (GGA+U ). We thereby examine the 3d series (M =Ti, V, Cr, Mn) as well as the 4d series (M =Mo, Ru, Rh) to discuss generic features in the electronic structure of hollandites first. Then, we in particular study the quasi-one-dimensional electron conduction observed in K [2,3] is discussed in this respect. We also study the electronic structure of K 2 V 8 O 16 to consider the origins of the observed anomalous electronic states and metal-insulator transition [4].

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Section: Introductionsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

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Anomalous electronic states of hollandite-type transition-metal oxides

Ohta

Toriyama

Sakamaki

et al. 2012

J. Phys.: Conf. Ser.

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“…Recently, chromium hollandite K 2 Cr 8 O 16 , which has the Cr ions with the average valence of Cr 3.75+ , was found to show a very rare metal-insulator transition keeping the ferromagnetism unchanged [1][2][3][4][5]. A chromium oxide NaCr 2 O 4 is one of the mixed-valent chromium oxide, which was reported to exhibit a colossal magnetoresistance effect [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure of Calcium-Ferrite-Type Cr Oxide NaCr₂O₄

Toriyama

Konishi

Ohta

2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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The density-functional-theory-based electronic structure calculations are made to clarify the electronic state of calcium-ferrite-type chromium oxide NaCr 2 O 4 . We show that the electronic structure near the Fermi level consists mainly of the 3d yz and 3d xz orbitals of Cr ions with strong admixture of the 2p z orbitals of corner O ions connecting the two zigzag double CrO chains. Thus, the basic electronic unit is not the zigzag double chain but the double rutile string; the latter is in the negative charge-transfer-gap situation and acquires a full ferromagnetic spin polarization caused by the double-exchange mechanism. The observed antiferromagnetism of NaCr 2 O 4 is a consequence of an alternating arrangement of the weakly-coupled ferromagnetic double rutile strings, which may give rise to the spin-flop transition and colossal magnetoresistance effect.

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“…A novel MI transition from the FM metallic to the FM insulating phases was reported to take place at T MI =95 K in the FM state below T C =180 K in K 2 Cr 8 O 16 with a rare mixed valence of Cr 3+ :Cr 4+ =2:6 (3d 2.25 ) [6]. In particular, the mechanism of the MI transition has attracted much attention from the experimental and theoretical point of views [6,10]. In both oxides, the orbital degree of freedom plays an important role for the magnetic and electric properties.…”

Section: Introductionmentioning

confidence: 99%