Non-Linear Effects in the Snoek Relaxation of Nb-O

Internal friction peaks measured as a function of temperature or frequency have been associated to non-linear processes only after studying how the amplitude of the applied stress affects the relaxation process. Here it is demonstrated that the partial derivative of the internal bidion with respect to the frequency at constant temperature is a useful tool to determine that non-linear effects are involved. This analysis applied to actual data of the Snoek relaxation in Nb-0, reveals that at high interstitial contents non-linear effects appear.