| Abstract | Neutron scattering measurements of the lowest-energy TO phonons in the relaxor Pb(Mg1/3Nb2/3)O3(PMN) are reported for 10<~T<~750K. The soft mode, which is overdamped by the polar nanoregions below the Burns temperature Td=620K, surprisingly recovers below 220 K. The square of the soft-mode energy (ħω0)2 increases linearly with decreasing temperature and is consistent with the behavior of a ferroelectric soft mode. At 10 K, ħω0 reaches 11 meV, the same value observed in ferroelectric Pb(Zn1/3Nb2/3)O3 at low T. An unusual broadening of the TA phonon starts at Td and disappears at 220 K, coincident with the recovery of the TO mode. These dynamics suggest that a well-developed ferroelectric state is established below 220 K. |
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