Abstract
Thin-film multilayered spin-glass CuMn/Cu structures exhibit glassy dynamics. The freezing temperature Tf was measured for 40 layers of CuMn films of thickness L =4.5,9.0 , and 20.0 nm, sandwiched between nonmagnetic Cu layers of thickness ≈60 nm. The Kenning effect, Tf∝ ln L , is shown to follow from power-law dynamics where the correlation length grows from nucleation as ξ(t,T)=c1a0(t/τ0)c2(T/Tg) , leading to [(Tf/Tg)c2 ln (tco/τ0)]+ ln c1= ln ( L /a0) . Here, Tg is the bulk spin-glass temperature, c1 and c2 are constants determined from the spin-glass dynamics, tco is the time for the correlation length to grow to the film thickness, τ0 is a characteristic exchange time ≈ℏ/kBTg , and a0 is the average Mn-Mn separation. For t≥tco , the magnetization dynamics are simple activated, with a single activation energy Δ max( L )/kBTg=(1/c2)[ ln ( L /a0)- ln c1] that does not change with time. Values for all these parameters are found for the three values of L explored in these measurements. We find experimentally Δ max( L )/kB=907 , 1246, and 1650 K, respectively, for the three CuMn thin-film multilayer thicknesses, consistent with power-law dynamics. Here, we perform a similar analysis based on the activated dynamics of the droplet model and find a much larger spread for Δ max( L ) than found experimentally.