Structural and electronic properties of thin Co films on Fe(001) and Fe(001)-p(1×1)O in the bct-to-hcp transition regime

We present a combined study of structural and electronic properties of thin Co films (up to 50 ML) grown on Fe(001). By means of primary-beam diffraction modulated electron emission, we found a structural transition between a strained bcc structure (bct) and the stable hcp phase occurring at ∼15 ML Co coverage. This structural change has a counterpart in the unoccupied electron states of the Co overlayer, as seen by absorbed current spectroscopy. We demonstrate that the evolution of AC spectra can be used to monitor the mentioned transition and apply this technique to the case of Co grown on Fe(001)-p(1×1)O. It is found that the presence of the oxygen causes a delayed onset of the bct–hcp transition.