Spin and charge states of Co in half-doped layered cobaltates La<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>1.5</mml:mn></mml:mrow></mml:msub></mml:math>Ca<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>0.5</mml:mn></mml:mrow></mml:msub></mml:math>CoO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>and La<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>1.5</mml:mn></mml:mrow></mml:msub></mml:math>Sr<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>0.5</mml:mn></mml:mrow></mml:msub></mml:math>CoO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>
この論文をさがす
説明
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.
収録刊行物
-
- Physical Review B
-
Physical Review B 86 2012-07-27
American Physical Society (APS)