The magnetic phase diagram of La2-xSr x Cu04 in the antiferromagnetic regime (x<0.02) has been derived from ,39 La nuclear quadrupole resonance studies from 4 to 250 K. The data demonstrate freezing of the doped holes' effective spin degrees of freedom below 7/~ (815 K)x into a spin-glass-like state which is superimposed on the antiferromagnetic background. These and previous results allow a detailed magnetic phase diagram to be constructed for x < 0.05 and reveal a distinct crossover at x ~ 0.02 in the nature of the spin-glass transition.

Dielectric spectra of the polyalcohols sorbitol and xylitol were measured under isobaric pressures up to 1.8 GPa. At elevated pressure, the separation between the alpha and beta relaxation peaks is larger than at ambient pressure, enabling the beta relaxation times to be unambiguously determined. Taking advantage of this, we show that the Arrhenius temperature dependence of the beta relaxation time does not persist for temperatures above T(g). This result, consistent with inferences drawn from dielectric relaxation measurements at ambient pressure, is obtained directly, without the usual problematic deconvolution the beta and alpha processes.