The magnetic effect on static nonlinear dielectric response in magnetic relaxor ferroelectrics

Abstract

The nonlinear dielectric response for the external field plays a very important role in providing useful information on relaxor ferroelectrics. Based on the spherical random-bond-random-field model and the Heisenberg model, considering the coupling interaction between the relaxor ferroelectricity and magnetism, we calculated the third-order static nonlinear dielectric susceptibility χ₃ as well as the scaled nonlinear susceptibility a₃=χ₃/χ₁⁴ of magnetic relaxor ferroelectrics. We find that in contrast to the electric field, the external magnetic field remains relaxor state being a glass state. As the temperature passes through the magnetic phase temperature T_c , χ₃ , similar to linear dielectric susceptibility χ₁ , deviates its original low temperature behavior and shows a sharp increase. Furthermore, the position of the peak of χ₃ and a₃ are greatly affected by T_c and h . The temperature of maximum χ₃ and a₃ shift to higher temperature region with increasing T_c and h , indicating that freezing temperature T_f of magnetic relaxor ferroelectrics might be controlled by magnetism through magnetoelectric coupling.