Abstract The hydration reaction of Ca A-type zeolite and calcium hydroxide was studied. The results revealed that an isostructural material of hydrocalumite (C-A-H) is generated at the early stage of hydration, and following that of strätlingite–vertumnite is generated. Only 0.77 nm of the C-A-H phase was observed at a humidity below 40% while part of the 0.77 nm phase swelled to 0.82 nm at a humidity of 40% or above.
The time decay of the thermoremanent magnetization(TRM) of the $\mbox{Fe}_{80-\mbox{x}}\mbox{Ni}_{\mbox{x}}\mbox{Cr}_{20}$ ($14\leq \mbox{x} \leq 30$) alloys has been measured for four different magnetic phases within the fcc $\mbox{$\gamma$}$-phase using a SQUID magnetometer. In the spin-glass phase(SG)(X=19) very distinct ageing effects are observed where M(t) can be described as $M(t)=M_0(t/t_{w})^{-\gamma}\exp[-(t/\tau)^{1-n}]$ for the entire time domain. In the reentrant spin-glass(RSG)(X= 23 and 26), M(t) can be better represented by the stretched exponential with an addition of a constant term which can be well explained by the Gabay-Toulouse(GT) model. We have also measured the linear and non-linear ac susceptibilities for the sample X=23 and confirmed the presence of the ferromagnetic(FM) ordering down to the lowest temperature. In the RSG(X=23), the TRM shows a minimum near T$_{\mbox{c}}$ and a local maximum just above T$_{\mbox{c}}$. In the FM phase (X=30) the popular prediction of the power law decay of the TRM is observed. The latter is indistinguishable from the stretched exponential in the antiferromagnetic(AF) phase (X=14).
Both Nd15Fe77B8 and Sm(CoCu)5 sintered magnets have been reported to exhibit staircase hysteresis loops with giant Barkhausen jumps below about 10 K. The pattern is reproducible at a fixed temperature. Here the observation of heat pulses associated with the magnetization jumps in Nd15Fe77B8 magnets is reported. The origin of these Barkhausen jumps in sintered magnets is discussed as a two-stage trigger/propagation process. The first stage may be dominated by magnetization reversal in volumes of δ3, where δ is the domain-wall thickness, as in the magnetic after effect, whereas the second stage reflects thermally induced domain-wall motion facilitated by the small lattice specific heat below about 10 K.
