arXiv 1606.016982016-06-06cond-mat.mtrl-scicond-mat.other

$HoFe_{1-x}Cr_xO_3$的带隙调谐和轨道介导的电子-声子耦合

Band gap tuning and orbital mediated electron phonon coupling in $HoFe_{1-x}Cr_xO_3$

Ganesh Kotnana, S. Narayana Jammalamadaka

发表信息：: J. Appl. Phys. 118, 124101 (2015)
DOI：: 10.1063/1.4931155

摘要：

我们报告证明轨道介导的电子-声子耦合和带隙调谐HoFe 1-xCrxO 3化合物。从室温拉曼散射，很明显，电子-声子耦合是敏感的存在下的Fe和Cr在B位。在670 cm ~（-1）附近，Fe ~（3+）-Cr ~（3+）之间发生了电荷转移，激活了一种类似Ag的局部氧呼吸模式，这一现象可以用Franck-Condon（FC）机制来解释。光学吸收研究表明，HoFe_（1-x）Cr_xO_3化合物中存在直接带隙。在带隙的减少，直到x = 0.5归因于作为由于在B位的Fe 3+和Cr 3+的诱导自旋无序的结果的氧的p轨道的加宽。相比之下，在x = 0.5以上的带隙的增加被解释的基础上，在导带处的Fe 3+的可用的未占据的d -轨道的减少。我们相信，上述结果将有助于基于正铁氧体的光电子器件的开发。

英文摘要：

We report on the evidenced orbital mediated electron phonon coupling and band gap tuning in HoFe1-xCrxO3 compounds. From the room temperature Raman scattering, it is apparent that the electron-phonon coupling is sensitive to the presence of both the Fe and Cr at the B-site. Essentially, an Ag like local oxygen breathing mode is activated due to the charge transfer between Fe3+ - Cr3+ at around 670 cm-1, this observation is explained on the basis of Franck-Condon (FC) mechanism. Optical absorption studies infer that there exists a direct band gap in the HoFe1-xCrxO3 compounds. Decrease in band gap until x = 0.5 is ascribed to the broadening of the oxygen p orbitals as a result of the induced spin disorder due to Fe3+ and Cr3+ at B site. In contrast, the increase in band gap above x = 0.5 is explained on the basis of the reduction in the available unoccupied d - orbitals of Fe3+ at the conduction band. We believe that above results would be helpful for the development of the optoelectronic devices based on the ortho-ferrites.

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