Abstract
Random electric fields (RF) due to charge disorder are at the origin of polar nanoregions (PNR) in the cubic relaxor PbMg1/3Nb2/3O3. They initiate Lacroix-Béné-type Cole-Cole semicircles, which achieve Cole-Davidson skew and dynamic power law criticality upon approaching superdipolar glass freezing. Below Tg ≈ 240 K percolation of PNR into microdomains is evidenced by interfacial creep and relaxation via Cole-Cole diagrams. Similar behavior occurs in uniaxial Sr0.8Ba0.2Nb2O6 (Tg ≈ 301 K). In contrast, matrix isolated ferromagnetic nanoparticles in CoFe/Al2O3 multilayers without RF interaction lack all of these effects except superglassy critical dynamics at Tg ≈ 46 K.
Acknowledgment
Thanks are due to Seweryn Miga for his assistance in the dielectric measurements.
Funding
The work at Katowice was supported by the Polish Ministry of Science and Higher Education under the project “Magnetic and ferroelectric multifunctional materials for electronics”.