Time-dependent specific heat below 1 K in the spin-density-wave state of (TMTSF)2PF6

Large time-dependence effects have been measured below 1 K in the specific heat of the spin-density-wave (SDW) compound (TMTSF${)}_2$ ${\mathrm{PF}}_6$, well below its glass transition temperature at 3.5 K. These effects indicate that most of the low-energy excitations characteristic of the disordered nature of the SDW subsystem are decoupled from the phonon bath for t≳1 s. A comparison is done with the related slow heat release observed over similar long time scales (up to ${10}^4$–${10}^5$ s) in structurally disordered materials. © 1996 The American Physical Society.