Charge-density waves and strain waves in thin epitaxial Cr(001) films on Nb

We have investigated the magnetic structure of thin epitaxial (001)-oriented Cr films grown on a Nb buffer layer on sapphire. By means of x-ray diffraction measurements the charge density waves (CDW) and strain waves (SW) in Cr film with thicknesses between 500 and 3000 {} have been studied. The results show that there exists an orientational pinning effect at both the Cr surface and the interface between Cr and the Nb buffer layer which causes an enlargement of the CDW-SW period, and a single q domain mode having a q vector pointing perpendicular to the surface. This pinning behavior relaxes wth increasing film thickness.