CONSTRUCTION OF A VERNIER TANDEM (3-PASS BRILLOUIN SPECTROMETER AND ITS APPLICATION TO SURFACE-ACOUSTIC-WAVE STUDY IN METALLIC MULTILAYER FILMS(3))

In order to study the elastic and magnetic properties of metallic mult ilayers by Brillouin scattering, we have constructed a (3+3)-pass vern ier tandem Fabry-Perot interferometer. We have also developed master/s lave and time-sharing techniques and electronics,to stabilize the inte rferometer during a long spectrum accumulation period of over several hours. In this report, we describe the details of the tandem spectrome ter and the control techniques. As an application of the tandem spectr ometer, we have studied sound velocity of Rayleigh surface waves exist ing in Ag/Cu multilayers as a function of the multilayer period. We ha ve observed considerable softening of more than 20% of the surface vel ocity as the multilayer period decreases from 150 angstrom to 7 angstr om.