Acoustic wave velocity in Ag/Fe nanolayers

The paper presents the results of acoustic wave velocity investigation in metallic Ag/Fe
nanolayers deposited on GaAs substrate. Measurements of velocity were performed using
femtosecond technique. Ag/Fe samples were characterized by different thickness of bilayers.
On the basis of experimental results of velocities, effective elastic constants $c_{11}$ were evaluated.
In the range of bilayers thickness above 80 Å the $c_{11}$ values are in accordance with
those calculated from the elastic constants of bulk materials (Rytov model). For lower values
of bilayer thickness elastic constants exhibit large decrease. Grimsditch’s model was applied
to interpret changes of elastic constants dependence for low bilayer thickness. This model
contains an additional interlayer treated as the parameter. Comparison the values of theoretical
elastic constants obtained by applying of Grimsditch model with those calculated from
experiment shows qualitative accordance in the range of small bilayer thickness.