PNNL

Abstract

The ²º7Pb nuclear system (nuclear spin I = 1/2; magnetic Moment µ ˜0.58 µN; isotopic abundance ˜ 22%) in ferroelectric solids has been proposed for a search for a Schiff moment associated with simultaneous violation of parity (P) and time-reversal invariance (T) in fundamental interactions [1] (see also a discussion of the sensitivity of such search in Ref. [2]). The idea is that, due to the Schiff moment, a ferroelectric sample would acquire a P,T-odd magnetic polarization along the direction of its electric polarization. In conclusion, we have presented the first experimental study of relaxation properties of ²º7Pb in PT and PZT below room temperature. We find that above T˜ 50 K, longitudinal relaxation rate follows the T² dependence characteristic of the two-phonon Raman process. On the other hand, as the temperature is decreased below T˜ 50 K, the longitudinal relaxation rates drop slower than ?T2 (as opposed to ?T7 expected for the Raman process), and the relaxation is probably due to a direct process associated with paramagnetic impurities and nuclear-spin diffusion. While the longitudinal relaxation times T1 vary between several seconds and over an hour in the temperature range between 290 and 10 K, the transverse relaxation time T2 is found to be ˜1.5 ms for all temperatures and all powder samples studied. D: we never discuss the origin of T2 relaxation. Maybe we should. 1.5 ms is only a bit shorter from what would be expected from nuclear spin-spin interactions. Any comments? At some point Sasha asked Oleg to calculate T2 exactly for PT and PZT, but I forgot what was the result. If such calculation exists, it would be great to compare with the expt. result. The obtained results provide an important input in the design of the experiments to search for P,T-violating effects in solid ferroelectrics