We present magnetic excitation spectra obtained for aligned crystals of Ba(Fe0.9Co0.1)2As2 with the superconducting transition temperature Tc ̃ 23 K. The simple comparison between these data and those of model calculations for the so-called Spp symmetry of the superconducting order parameter indicates that the peak width of the spectra observed at the M point can be explained by the symmetry, although the material parameters used in the calculation may have certain ambiguity. Arguing the results in more detail, we point out that the possibility of the Spp symmetry cannot be excluded as the one realized in this Fe pnictide superconductor. It is consistent with our previous finding that the rate of Tc-suppression by nonmagnetic impurities is much smaller than the value expected for the Spp symmetry. It suggests the existence of a new pairing mechanism in Fe pnictide superconductors.
- Magnetic excitation
- Superconducting symmetry