Non-linear dielectric dispersion in PMN relaxor system

In PbMg1/3Nb2/3O3 (PMN) single crystals the first ε1* and the third harmonic complex dielectric constant ε3* were measured along the 〈0 0 1〉 and 〈1 1 1〉 axes as a function of frequency and temperature in a small electric field. In the temperature interval between 270 and 220 K the first ε1* and the third harmonic complex dielectric constant ε3*, and the dielectric non-linearity β=ε3/ε14ε03 show prominent dielectric dispersion. It is also shown that the dielectric non-linearity β shows a crossover from a decreasing paraelectric-like to a rapidly increasing glass-like temperature behaviour which was predicted by the spherical random bond random field model for relaxors.