Institut Max von Laue-Paul Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France.
J Phys Condens Matter. 2010 Aug 11;22(31):315701. doi: 10.1088/0953-8984/22/31/315701. Epub 2010 Jul 9.
To shed light on the role of magnetism on the superconducting mechanism of the oxygen-free FeAs pnictides, we investigate the effect of magnetic ordering on phonon dynamics in the low-temperature orthorhombic parent compounds, which present a spin density wave. The study covers both the 122 (AFe(2)As(2); A = Ca, Sr, Ba) and 1111 (AFeAsF; A = Ca, Sr) phases. We extend our recent work on the Ca (122 and 1111) and Ba (122) cases by treating, computationally and experimentally, the 122 and 1111 Sr compounds. The effect of magnetic ordering is investigated through detailed non-magnetic and magnetic lattice dynamical calculations. The comparison of the experimental and calculated phonon spectra shows that the magnetic interactions/ordering have to be included in order to reproduce well the measured density of states. This highlights a spin-correlated phonon behavior which is more pronounced than the apparently weak electron-phonon coupling estimated in these materials. Furthermore, there is no noticeable difference between phonon spectra of the 122 Ba and Sr, whereas there are substantial differences when comparing these to CaFe(2)As(2) originating from different aspects of structure and bonding.
为了阐明磁场对氧自由的 FeAs 磷化物超导机制的作用，我们研究了磁有序对低温正交母体化合物中声子动力学的影响，这些母体化合物呈现自旋密度波。这项研究涵盖了 122（AFe(2)As(2)；A = Ca，Sr，Ba）和 1111（AFeAsF；A = Ca，Sr）相。我们通过对 Ca（122 和 1111）和 Ba（122）案例进行计算和实验处理，扩展了我们最近关于 Ca（122 和 1111）和 Ba（122）的工作，研究了 122 和 1111 的 Sr 化合物。通过详细的非磁性和磁性晶格动力学计算来研究磁有序的影响。实验和计算声子谱的比较表明，为了很好地重现测量的态密度，必须包括磁相互作用/有序。这突出了一种与自旋相关的声子行为，比这些材料中估计的显然较弱的电子-声子耦合更为明显。此外，122 的 Ba 和 Sr 的声子谱之间没有明显差异，而当将它们与 CaFe(2)As(2)进行比较时，由于结构和键合的不同方面，存在实质性差异。
