Ouyang Z W, Matsuda Y H, Nojiri H, Inada Y, Niwa Y, Arima T
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
J Phys Condens Matter. 2009 Jan 7;21(1):016006. doi: 10.1088/0953-8984/21/1/016006. Epub 2008 Dec 2.
Evolution of the Mn K-edge x-ray absorption near edge structure (XANES) in Pr(0.6)Ca(0.4)MnO(3) at pulsed magnetic fields has been investigated. A small enhancement of XANES spectra is detected across the magnetic-field-induced transition from the charge- and orbital-ordered (COO) insulator to ferromagnetic metal at 20 K. It is found that the magnetic-field dependence of the enhancement shows clear hysteresis, as seen in the magnetization with metamagnetic transition, suggesting a significant correlation between the change in the XANES and the field-induced collapse of the COO state. The enhancement of the absorption can be explained by an increase of the 4p density of states due to a reduction of hybridization between the 4p state of the central Mn ion with the core hole and the neighboring Mn 3d state. Local structural change around Mn ions is expected to modify the strength of the hybridization.
研究了脉冲磁场下Pr(0.6)Ca(0.4)MnO(3)中锰K边X射线吸收近边结构（XANES）的演化。在20K时，从电荷和轨道有序（COO）绝缘体到铁磁金属的磁场诱导转变过程中，检测到XANES光谱有小幅增强。发现这种增强的磁场依赖性表现出明显的磁滞现象，如同变磁转变中的磁化情况一样，这表明XANES的变化与COO态的场致崩塌之间存在显著关联。吸收的增强可以通过中心锰离子的4p态与芯孔和相邻锰3d态之间杂化作用的减弱导致4p态密度增加来解释。预计锰离子周围的局部结构变化会改变杂化作用的强度。
