Phase transitions and magnetoelectroelastic instabilities in Pb(Fe_(1/2)Nb_(1/2))O_3 multiferroic ceramics

摘要

Magnetoelectric coupling can be observed in multiferroic materials in the regions where magnetic and ferroelectric ordering coexist and in many cases is mediated via lattice strain. Pb(Fe_(1/2)Nb_(1/2))O_33 (PFN) is a well-known multiferroic, presenting ferroelectric ordering (below T_c = 380 K) and a Neel temperature (antiferromagnetic ordering) T_n = 143 K. However, recent experimental results suggest that PFN can display ferromagnetic ordering at higher temperatures and a still unclear sequence of phase transitions. In this work, high-density PFN ceramics were prepared by a conventional ceramic method. Dielectric, magnetic and anelastic responses were measured as a function of temperature. The experimental results present complementary evidence of anomalies (additional to those which can be directly associated with the reported transitions at T_c and T_N) which cold be associated with a structural phase transition (T~ 315 K), an antiferromagnetic-ferromagnetic phase transition (110 K) and magnetoelectroelastic instabilities around 250 K.