Barkhausen noise, including both periodic and aperiodic components, is found in and near the relaxor regime of a familiar relaxor ferroelectric, ${\mathrm{PbMg}}_{1/3}{\mathrm{Nb}}_{2/3}{O}_3$, driven by a periodic electric field. The temperature dependences of both the amplitude and spectral form show that the size of the coherent changes in the dipole moment shrink as the relaxor regime is entered, contrary to expectations based on some simple models.

• Received 9 July 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.017601