Frustration of Exchange-Striction Ferroelectric Ordering and Growth of Electric Polarization of Phase Separation Domains in R.sub.0.8Ce.sub.0.2Mn.sub.2O.sub.5 Solid Solutions

The effect of rare-earth ions (R = Er.sup.3+, Tb.sup.3+, and Ce.sup.3.75+) on the dielectric properties and the electric polarization induced by local polar phase separation domains in solid solutions of R.sub.0.8Ce.sub.0.2Mn.sub.2O.sub.5 (R = Er, Tb) multiferroics has been studied. These parameters are found to qualitatively differ from those of initial RMn.sub.2O.sub.5 (R = Er, Tb) crystals studied before. It is shown that the properties of the polar phase separation domains that form in a subsystem of Mn.sup.3+ and Mn.sup.4+ ions due to a finite probability of tunneling electrons between these ions with different valences are substantially dependent on the values of crystal fields in which these domains exist. A combined influence of Er.sup.3+, Tb.sup.3+, and Ce.sup.3.75+ ions is found to substantially change the crystal field in R.sub.0.8Ce.sub.0.2Mn.sub.2O.sub.5 (R = Er, Tb) as compared to RMn.sub.2O.sub.5 (R = Er, Tb).