Finite-size effects in thin Ag-Mn spin-glass layers.

Abstract

Measurements of the quasistatic spin-freezing temperature ${\mathit{T}}_{\mathit{f}}$, as a function of spin-glass layer thickness, ${\mathit{W}}_{\mathrm{Ag}\mathrm{\ensuremath{-}}\mathrm{Mn}}$, are presented for multilayer samples of the spin-glass ${\mathrm{Ag}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$ (x=0.04 and 0.09) alternated with interlayers of Ag or Cu having thickness ${\mathit{W}}_{\mathrm{il}}$=30 nm, a value large enough to magnetically decouple the spin-glass layers. The values of ${\mathit{T}}_{\mathit{f}}$ are independent of whether the interlayer metal is Ag or Cu, and thus insensitive to grain sizes and structural details of spin-glass--interlayer interfaces. To within experimental uncertainty, for a given value of ${\mathit{W}}_{\mathrm{SG}}$, the ratio ${\mathit{T}}_{\mathit{f}}$/${\mathit{T}}_{\mathit{f}}^{\mathit{b}}$ (${\mathit{T}}_{\mathit{f}}^{\mathit{b}}$ is the bulk transition temperature for a given x) for ${\mathrm{Ag}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$ is independent of x and the same as was previously found for Cu-Mn. The data for thin (${\mathit{W}}_{\mathrm{SG}}$\ensuremath{\le}10 nm) spin-glass layers are compatible with the predictions of the Fisher-Huse droplet-excitation model. Under some circumstances, large-angle x-ray scattering is shown to directly measure the layer thickness of the thinner of the two constituents of a multilayer sample.