2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/221322Spin relaxation close to the glass temperature of CuMn and AuFe spin glasses is shown, by neutron spin echo, to follow a generalised exponential function which explicitly introduces hierarchically constrained dynamics and macroscopic interactions. The interaction parameter is directly related to the normalised Tsallis non-extensive entropy parameter, q, and exhibits universal scaling with reduced temperature. At the glass temperature q=5/3 corresponding, within Tsallis' q-statistics, to a mathematically defined critical value for the onset of strong disorder and non-linear dynamics.4 pages: accepted for publication in Physical Review Letters (Feb 2009)Disordered Systems and Neural NetworksOther Condensed Mattertext