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 Tc , 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 Tc and h . The temperature of maximum χ3 and a3 shift to higher temperature region with increasing Tc and h , indicating that freezing temperature Tf of magnetic relaxor ferroelectrics might be controlled by magnetism through magnetoelectric coupling.