Critical magnetic behavior in [Ag8/Co0.5]x64, [Ag8/Co1]x32 and [Ag16/Co1]x32 epitaxial multilayers

We investigate the low temperature magnetic behavior of three epitaxial Co/Ag multilayers, grown onto MgO (001) substrates, with a nominal content per period either half monolayer or one Co, and 8 16 Ag monolayers. The samples were studied by X-ray reflectivity diffraction, transmission electron microscopy, magnetometry ac susceptometry. results indicated well defined stacking sequence in growth direction, number periods monolayers being coincident values for each sample. Co layers found to be discontinuous corresponded quasi-monodisperse in-plane distribution nanoparticles embedded Ag(001) matrix. zero-field cooled field variations magnetization presence irreversibilities at temperatures below 20 K. frequency (f) (T) dependencies real part susceptibility (??) Vogel–Fulcher samples, shift parameter (?) order 4 x 10-2. For sample, experimental data corresponding imaginary (??) f T collapse into single curve according dynamic scaling law. Taken together, these allow us conclude that multilayers experience phase transition paramagnetic superspin glass type, driven dipolar interactions between nanoparticles. Regarding influence multilayer features, we clear dependence on period.