Specific-heat evidence of strong electron correlations and thermoelectric properties of the ferromagnetic perovskite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi><mml:mi mathvariant="normal">Co</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

Balamurugan, S.; Yamaura, Kazunari; Karki, Amar B.; Young, David P.; Arai, M.; Takayama‐Muromachi, E.

doi:10.1103/physrevb.74.172406

Cited by 82 publications

(55 citation statements)

References 15 publications

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“…9(b), B], originating from the fully oxidized SCO 3 phase. 57) The saturation magnetization at 10 K [inset of Fig. 9(b)] was 2.0¯B/Co, which is almost the same as that of bulk SCO 3 (³2.1¯B/Co).…”

Section: ¹3supporting

confidence: 52%

Transition-metal-oxide based functional thin-film device using leakage-free electrolyte

Katase

Ohta

2017

J. Ceram. Soc. Japan

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Using the flexible valence states of transition-metal-oxides (TMOs), the optical, electronic, and magnetic properties can be simultaneously controlled by electrochemical oxidation and reduction. Herein we review our recent works on the electrochemically switchable functional thin-film device, which has a three-terminal thin-film-transistor (TFT) structure with the TMO as an active channel layer and the liquid-leakage-free electrolyte as a gate insulator. Thin films of vanadium dioxide, tungsten trioxide, and strontium cobaltite were selected as the channel layer. By applying the gate voltage at room temperature in air, the protonation/ deprotonation or oxidation/deoxidation occurs in the TMO channels and their opto-electronic and electro-magnetic properties are reversibly switched by using the mobile ions in the solid TFT structure. The present device with liquid-leakage-free electrolyte provides a novel design concept for the development of future multifunctional switching devices based on TMOs.

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Section: ¹3supporting

confidence: 52%

Transition-metal-oxide based functional thin-film device using leakage-free electrolyte

Katase

Ohta

2017

J. Ceram. Soc. Japan

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“…[35] The shift of 0.2 eV as strain increases to 4.2% is consistent with the transition from SrCoO 2.9 to SrCoO 2.75 determined in previous studies for bulk P-SCO. [36] An investigation of the Co-L edge in [37] Using this shift, we can estimate a transfer here of up to 0.4 e -, which is compatible with ∆δ ≤ 0.20 as the equilibrium state transitions from SrCoO 2.9 to SrCoO 2.75 with tensile strain. Quantification of the oxygen non-stoichiometry is given in Figure 3.…”

Section: Oxygen Stoichiometry Changes Probed By X-ray Absorption Specmentioning

confidence: 69%

“…Since it has been shown that the double exchange mechanism thought responsible for the metallic behavior of P-SCO is disrupted when δ ≥ 0.1, we can place an upper bound on δ at this level when 1% tensile strain is supplied to the film. [36,41] At mismatches that induce even greater tensile strains, the transition to an increasingly insulating nature implies that δ > 0.1 and that δ is increasing with such strain. Consistent with the XAS and magnetic data, none of the films (even with strain) exhibit behaviors that imply δ > 0.25 or the BM-SCO phase; in comparison to the resistivity of a previously-deposited 14 nm BM-SCO film on STO, all annealed P-SCO films have values orders of magnitude lower up to room temperature.…”

Section: Evolution Of Magnetic and Electrical Transport Properties Wimentioning

confidence: 99%

Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Petrie

Mitra

Jeen

et al. 2016

Adv Funct Materials

215

160

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The ability to manipulate oxygen anion defects rather than metal cations in complex oxides is facilitating new functionalities critical for emerging energy and device technologies.However, the difficulty in activating oxygen at reduced temperatures hinders the deliberate control of an important defect, oxygen vacancies. Here, strontium cobaltite (SrCoO x ) is used to demonstrate that epitaxial strain is a powerful tool for manipulating the oxygen vacancy concentration even under highly oxidizing environments and at annealing temperatures as low as 300 °C. By applying a small biaxial tensile strain (2%), the oxygen activation energy barrier decreases by ~30%, resulting in a tunable oxygen deficient steady-state under conditions that would normally fully oxidize unstrained cobaltite. These strain-induced changes in oxygen stoichiometry drive the cobaltite from a ferromagnetic metal towards an antiferromagnetic insulator. The ability to decouple the oxygen vacancy concentration from its typical dependence on the operational environment is useful for effectively designing oxides materials with a specific oxygen stoichiometry.2

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“…This is caused by hole doping via oxygen intercalation and is consistent with hole carriers in stoichiometric SrCoO 3 . [27,33] In summary, high quality BM-SCO epitaxial thin films were successfully grown on STO While the P-SCO film shows a higher magnetization value than that of the Mix-SCO film, both films reveal the same T c (~200 K). This confirms that the Mix-SCO film contains a mixture of BM-and P-phases, which were indicted from the XRD results.…”

Section: Changes In the Magnetic Properties By Valence State Modificamentioning

confidence: 99%

Topotactic Phase Transformation of the Brownmillerite SrCoO_2.5 to the Perovskite SrCoO_3–_δ

et al. 2013

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Oxygen stoichiometry is one of the most important elements in determining the physical properties of transition metal oxides (TMOs). A small change in the oxygen content results in the variation of valence state of the transition metal, drastically modifying the materials functionalities. The latter includes, for instance, (super-)conductivity, magnetism, ferroelectricity, bulk ionic conduction, and catalytic surface reactions. [1][2][3][4][5] In particular, among those applications, TMOs with mixed valence states have attracted attention for many environmental and renewable energy applications, including catalysts, hydrogen generation from water splitting, cathodes in rechargeable batteries and solid oxide fuel cells, and oxygen separation membranes. [6][7][8] For example, previous studies have shown that the ability to control the number of d-band electron population and detailed spin configuration in TMOs is critical for improved catalytic performance of TMOs. [9,10] In this context, SrCoO x (2.5 ≤ x ≤ 3.0) is an ideal class of materials to study the evolution of the physical properties by modifying the valence state in TMOs, due to the existence of two structurally distinct topotactic phases, i.e. the brownmillerite SrCoO 2.5 (BM-2 SCO) (see Figure 1a) and the perovskite SrCoO 3 . [11,12] Especially, BM-SCO has atomicallyordered one-dimensional vacancy channels (see Figure 1a), which can accommodate additional oxygen when the valence state of Co is changed. Moreover, SrCoO x exhibits a wide spectrum of physical properties from antiferromagnetic insulator to ferromagnetic metal depending on the oxygen stoichiometry. [11][12][13] Since SrCoO x has only a single control knob, i.e. the oxygen contentx, to modify the Co valence state without cation doping, it is straightforward to study the valence state (i.e. oxygen content) dependent physical properties. However, so far, the growth of high quality single crystalline materials has not been as successful due to difficulty in controlling the right oxidation state.In this work, we report on the epitaxial growth of high quality BM-SCO single crystalline films on SrTiO 3 (STO) substrates by pulsed laser epitaxy (PLE). In order to examine the topotactic phase transformation to the perovskite SrCoO 3- (P-SCO), some of the samples were subsequently in-situ annealed at various oxygen pressure (P(O 2 )) to fill the oxygen vacancies.While the direct growth of P-SCO films with x = 3.0 was an arduous task, we found that postannealing in high P(O 2 ) (> several hundreds of Torr) could fill sufficient amount of oxygen vacancies, yielding systematic evolution in electronic, magnetic, and thermoelectric properties. (Figure 1b) demonstrate that the films are of high quality. X-ray rocking curve ω-scans revealed a full width half maximum (FWHM) of < 0.04º, demonstrating the excellent crystallinity (cf., FWHM of the 002 STO peak was ~0.02º) of our films (data not shown).While we have shown the XRD data from a well-optimized, high quality thin film, it is worthwhile to mention tha...

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Specific-heat evidence of strong electron correlations and thermoelectric properties of the ferromagnetic perovskiteSrCoO3−δ

Cited by 82 publications

References 15 publications

Transition-metal-oxide based functional thin-film device using leakage-free electrolyte

Transition-metal-oxide based functional thin-film device using leakage-free electrolyte

Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Topotactic Phase Transformation of the Brownmillerite SrCoO_2.5 to the Perovskite SrCoO_3–_δ

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Specific-heat evidence of strong electron correlations and thermoelectric properties of the ferromagnetic perovskiteSrCoO3−δ

Cited by 82 publications

References 15 publications

Transition-metal-oxide based functional thin-film device using leakage-free electrolyte

Transition-metal-oxide based functional thin-film device using leakage-free electrolyte

Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Topotactic Phase Transformation of the Brownmillerite SrCoO2.5 to the Perovskite SrCoO3–δ

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Topotactic Phase Transformation of the Brownmillerite SrCoO_2.5 to the Perovskite SrCoO_3–_δ