Heat release and time-dependent thermal expansion of NbTi(D)

Glasslike anomalies of low-temperature thermal properties were observed for polycrystalline NbTi doped with deuterium. The distribution parameter of two-level systems (TLS) determined from heat release data is about 40 times larger than that for vitreous silica. After rapid cooling together with a long-time heat release a time-dependent change of sample length was detected. The dependence of length relaxation on time as well as on starting temperature before cooling corresponds to the heat release data. The coefficient of the thermal expansion of the TLS is negative.