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首页> 外文期刊>Physical review >Spin and charge states of Co in half-doped layered cobaltates La_(1.5)Ca_(0.5)CoO_4 and La_(1.5)Sr_(0.5)C_oO_4
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Spin and charge states of Co in half-doped layered cobaltates La_(1.5)Ca_(0.5)CoO_4 and La_(1.5)Sr_(0.5)C_oO_4

机译:半掺杂层状钴La_(1.5)Ca_(0.5)CoO_4和La_(1.5)Sr_(0.5)C_oO_4中Co的自旋和电荷态

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摘要

We have investigated the charge dynamics and local spin state in half-doped layered cobaltates La_(1.5)Ca_(0.5)CoO_4 and La_(1.5)Sr_(0.5)CoO_4. By examining temperature-dependent infrared-active phonon modes, we found clear signatures of the structural distortion related to the spin-state transition around T_s = 400-600 K. While the kinetic energy of the electronic system, estimated by the low-energy spectral weight in the optical conductivity spectrum, as well as the optical gap energy is strongly affected by the charge-order instability, it shows a noticeable enhancement upon the spin-state transition which is attributed to the release of the spin blockade of the electron hopping between the low-spin (Co~(3+)) and high-spin (Co~(2+)) states. These understandings of the spin state are further evidenced by the reexamination of high-temperature Seebeck coefficient-and magnetic susceptibility.
机译:我们研究了半掺杂层状钴La_(1.5)Ca_(0.5)CoO_4和La_(1.5)Sr_(0.5)CoO_4的电荷动力学和局部自旋态。通过检查温度相关的红外活性声子模式,我们发现与T_s = 400-600 K左右的自旋态跃迁有关的结构畸变的清晰特征。而电子系统的动能由低能谱估算光导谱中的重量以及光隙能量受电荷阶数不稳定性的强烈影响,在自旋态跃迁上显示出明显的增强,这归因于电子跃迁之间的自旋阻断的释放低旋转(Co〜(3+))和高旋转(Co〜(2+))状态。对高温塞贝克系数和磁化率的重新检验进一步证明了对自旋态的这些理解。

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  • 来源
    《Physical review》 |2012年第4期|p.045133.1-045133.6|共6页
  • 作者单位

    Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan Department of Photonics and Applied Physics, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea;

    Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan;

    Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan;

    Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan Cross-Correlated Materials Research Group (CMRG) and Correlated Electron Research Group (CERG),ASI, RIKEN, Wako 351-0198, Japan Multiferroics Project, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST),Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan;

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  • 正文语种 eng
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  • 关键词

    optical properties of bulk materials and thin films; infrared and raman spectra;

    机译:散装材料和薄膜的光学性能;红外光谱和拉曼光谱;

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