Magnetic Structure of SrCoO<sub>2.5</sub>

Takeda, Tomo; Yamaguchi, Yasuo; Watanabe, Hiroshi

doi:10.1143/jpsj.33.970

Cited by 125 publications

(94 citation statements)

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“…Note the latter have T N = 570 K. [11,26] This bulk-like behavior clearly indicates that our BM-SCO epitaxial thin films are homogeneously grown without any oxygen enriched SCO phases or paramagnetic impurities, [27,28] consistent with our XRD results. On the other hand, the oxygen post-annealed films showed clear evidence of ferromagnetism (Figure 4a, b).…”

Section: Changes In the Magnetic Properties By Valence State Modificasupporting

confidence: 83%

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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Section: Changes In the Magnetic Properties By Valence State Modificasupporting

confidence: 83%

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

et al. 2013

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“…The broad range of transition metal oxide functionalities, including superconductivity, magnetism, and ferroelectricity, can be tuned by the careful choice of parameters such as strain, oxygen content, or applied electric and magnetic fields [1][2][3][4][5][6][7][8][9] . This tunability makes transition metal oxide materials ideal candidates for use in developing novel information and energy technologies 10,11 .…”

mentioning

confidence: 99%

“…The system undergoes well-defined structural phase transitions between distinct topotactic phases, from a cubic perovskite phase at SrCoO 3 to brownmillerite SrCoO 2.5 . The ties between the structural and functional properties of the material are obvious as a magnetic phase transition from ferromagnetic (FM) SrCoO 3.0 with T C = 280-305 K to antiferromagnetic (AFM) SrCoO 2.5 with T N = 570 K accompanies the structural transition 5,[12][13][14] . This is similar to the case of SrFeO 3−δ , which has also been demonstrated to undergo oxygen vacancy ordering with magnetic phase transitions related to the structure and Fe charge ordering [17][18][19] .…”

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confidence: 99%

Strain-induced magnetic phase transition inSrCoO3−δthin films

Callori

Bertinshaw

et al. 2015

Phys. Rev. B

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It has been well established that both in bulk at ambient pressure and for films under modest strains, cubic SrCoO 3−δ (δ < 0.2) is a ferromagnetic metal. Recent theoretical work, however, indicates that a magnetic phase transition to an antiferromagnetic structure could occur under large strain accompanied by a metal-insulator transition. We have observed a strain-induced ferromagnetic to antiferromagnetic phase transition in SrCoO 3−δ films grown on DyScO3 substrates, which provide a large tensile epitaxial strain, as compared to ferromagnetic films under lower tensile strain on SrTiO3 substrates. Magnetometry results demonstrate the existence of antiferromagnetic spin correlations and neutron diffraction experiments provide a direct evidence for a G-type antiferromagnetic structure with Neél temperatures between TN ∼ 135 ± 10 K and ∼ 325 ± 10 K depending on the oxygen content of the samples. Therefore, our data experimentally confirm the predicted strain-induced magnetic phase transition to an antiferromagnetic state for SrCoO 3−δ thin films under large epitaxial strain.The broad range of transition metal oxide functionalities, including superconductivity, magnetism, and ferroelectricity, can be tuned by the careful choice of parameters such as strain, oxygen content, or applied electric and magnetic fields 1-9 . This tunability makes transition metal oxide materials ideal candidates for use in developing novel information and energy technologies 10,11 . SrCoO 3 is a particularly interesting system for investigation. SrCoO 3−δ has long been studied due to its propensity to form oxygen-vacancy-ordered structures as the oxygen content is decreased. The system undergoes well-defined structural phase transitions between distinct topotactic phases, from a cubic perovskite phase at SrCoO 3 to brownmillerite SrCoO 2.5 . The ties between the structural and functional properties of the material are obvious as a magnetic phase transition from ferromagnetic (FM) SrCoO 3.0 with T C = 280-305 K to antiferromagnetic (AFM) SrCoO 2.5 with T N = 570 K accompanies the structural transition 5,[12][13][14] . This is similar to the case of SrFeO 3−δ , which has also been demonstrated to undergo oxygen vacancy ordering with magnetic phase transitions related to the structure and Fe charge ordering [17][18][19] .In addition to oxygen stoichiometry, other possibilities, such as strain or applied magnetic or electric fields, may be used to tune the system. Lee and Rabe have simulated the effect of epitaxial strain on SrCoO 3.0 and predict a large polar instability resulting in a dependence of the magnetic structure on strain 20,21 . Their results show that the magnetic state can be controlled by the amount of compressive or tensile strain applied. An AFM-FM transition is predicted at both, tensile strain of ∼2.0 % and compressive strain of approximately -0.8 %, which is caused through the Goodenough-Kanamori rules as a consequence of simultaneous structural phase transitions between phases with different distortions and rotational pa...

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“…3d, A), suggesting the AFM nature of SrCoO 2.5 . [20] It should be noted that it is difficult to judge the AFM state in the virgin SrCoO 2.5 layer only from the magnetic properties in Fig. 3d; considering that (1) it is a known fact that the brownmillerite SrCoO 2.5 is an AFM insulator with T N = 570 K, [20] (2) it is confirmed that the SrCoO 2.5 layer is an insulator with the brownmillerite structure, in which the alternately stacked structure of CoO 4 tetrahedra and CoO 6 octahedra layers are clearly observed ( Fig.…”

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confidence: 99%

“…[20] It should be noted that it is difficult to judge the AFM state in the virgin SrCoO 2.5 layer only from the magnetic properties in Fig. 3d; considering that (1) it is a known fact that the brownmillerite SrCoO 2.5 is an AFM insulator with T N = 570 K, [20] (2) it is confirmed that the SrCoO 2.5 layer is an insulator with the brownmillerite structure, in which the alternately stacked structure of CoO 4 tetrahedra and CoO 6 octahedra layers are clearly observed ( Fig. S1), and (3) the magnetic susceptibility of the SrCoO 2.5 layer is one order of magnitude smaller than that estimated by Curie's law of paramagnetism [30] and consistent with that previously reported in brownmillerite SrCoO 2.5 film with AFM state, [31] the virgin SrCoO 2.5 layer is considered to be AFM state rather than paramagnetic state.…”

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confidence: 99%

Reversibly Switchable Electromagnetic Device with Leakage‐Free Electrolyte

Katase

Suzuki

Ohta

2016

Adv Elect Materials

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A reversibly switchable electromagnetic oxide device is demonstrated by using a thin-film transistor structure with a newly developed "leakage-free electrolyte" as a gate insulator. The electrical and magnetic behavior of the device can be switched from antiferromagnetic insulation to ferromagnetic metal electrically under DC voltage of ±3 V at room temperature.The result provides a novel design concept for practical memory device.

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Magnetic Structure of SrCoO_2.5

Cited by 125 publications

References 10 publications

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

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

Strain-induced magnetic phase transition inSrCoO3−δthin films

Reversibly Switchable Electromagnetic Device with Leakage‐Free Electrolyte

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Magnetic Structure of SrCoO2.5

Cited by 125 publications

References 10 publications

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

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

Strain-induced magnetic phase transition inSrCoO3−δthin films

Reversibly Switchable Electromagnetic Device with Leakage‐Free Electrolyte

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Product

Resources

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Magnetic Structure of SrCoO_2.5

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

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