Pulsed dielectric spectroscopy of supercooled liquids

Positron annihilation response and broadband dielectric spectroscopy: Propylene carbonate

“…The activity of the 22 Na source was 4 MBq. The radioactive positron 22 Na source plus samples assembly was kept under vacuum in a rotary pump. During the low-temperature measurements from 15 up to 300 K samples in a holder were fixed at the end of a cold finger of a closed-cycle helium gas refrigerator Leybold with automatic temperature regulation.…”

“…Broadband dielectric spectra of the same PC batch have been collected using a combination of different techniques to cover nearly 20 decades in frequency [15,[20][21][22][23][24]. The lowest frequencies (10 Hz < m < 1 kHz) were investigated with a time-domain spectrometer [22].…”

Magnetic properties of Cr–Fe–Mn alloys

“…It was pointed out [23], but previously not observed, that such a mechanism might also lead to upturns during relaxation of magnetic systems. Apart from the possible role of such memory effects, we propose that the upturns on the TRM curves for Cr 77 Fe 21 Mn 2 and Cr 68 Fe 22 Mn 10 of Fig.…”

“…In the case of dielectric relaxation, mentioned above, the upturns were explained in terms of a ''memory effect'', introduced during the relaxation process of a system containing a distribution of relaxation times, by stepping the height of an externally applied electric field pulse down to a lower value after a specific time duration [23]. It was pointed out [23], but previously not observed, that such a mechanism might also lead to upturns during relaxation of magnetic systems.…”

“…4(a), have not been reported in similar measurements on binary Cr 100Àx Fe x alloys having x ¼ 17, 22 [21] and 21 [22], or to our knowledge, having other Fe concentrations. In this regard it is worth mentioning that upturn effects are also observed [23] for the dielectric relaxation of supercooled liquids in response to complex electric field and temperature histories during pulsed dielectric spectroscopy experiments.…”