ELECTRON-SPIN-RESONANCE LINEWIDTH OF MULTILAYERED CUMN/CU SPIN-GLASSES - RESIDUAL WIDTH AND THERMAL-BROADENING COEFFICIENT

The electron-spin-resonance (ESR) linewidth DELTAH(T) has been measured in multilayered Cu1-xMnx/Cu (x = 0.07,0.11) as a function of spin-glass layer thickness W(SG) (1 nm less-than-or-equal-to W(SG) less-than-or-equal-to 1000 nm). For temperatures well above the freezing temperature T(f), DELTAH (T) = A + BT, where A is the residual linewidth and B the thermal-broadening coefficient. The residual linewidth increases with decreasing W(SG), indicating that the paramagnetic Curie-Weiss temperature THETA and/or the inhomogeneous broadening depend on W(SG). Preliminary high-temperature-susceptibility measurements confirm that theta decreases with decreasing W(SG), but are not sensitive enough to determine quantitatively if this change is entirely responsible for the observed changes in A. The thermal-broadening coefficient B characterizes the strength of the ESR bottleneck. As W(SG) decreases, B increases, indicating the breaking of the bottleneck via the presence of additional relaxation paths. Possible mechanisms for these paths are suggested. The increase in B with decreasing W(SG) is similar to that observed with increasing concentration of a third element in bulk spin glasses. Possible links between decreasing W(SG) and increasing anisotropy are considered. Data parametrized in terms of epsilon, where epsilon = [T(f)(infinity)-T(f)(W(SG)]/T(f)(infinity), show that both A and B increase linearly with increasing epsilon over the entire range of epsilon studied.