The emergence of magnetic properties in (Pb_(0.845)Sm_(0.08)Fe_(0.035))(Ti_(0.98)Mn_(0.02))O_3 and (Pb_(0.88)Nd_(0.08))(Ti_(0.98)Mn_(0.02))O_3 perovskite ceramics

摘要

The emergence of magnetic properties and quadratic magnetoelectric coupling in a material with outstanding ferroelectric properties has been pursued. Thus, the multiferroicity driven by the substitution of rare earth R~(3+) ions (R = Sm, Nd) on the A-site of PbTiO_3 perovskite ceramics has been investigated. In some samples, a transition element with large ionic radius, like Fe~(2+), has been also added on the A site. Polycrystalline ceramic samples with composition (Pb_(1-3x/2-y)R_xFe_y) (Ti_(0.98)Mn_(0.02))O_3 (R = Sm; x = 0.08, y = 0.035) and (Pb_(1-3x/2)R_x)(Ti_(0.98)Mn_(0.02)O_3 (R = Nd, x = 0.08) have been prepared by conventional solid state ceramic processing, starting from reagent grade oxide powders. X-ray diffraction analysis confirmed the obtaining of a crystalline phase with tetragonal P4 mm symmetry. Transmission electron microscopy and high resolution transmission electron microscopy investigations have been carried out in order to analyze the local structure. Temperature dependence of dielectric permittivity revealed a strong anomaly at the temperature T_c of the paraelectric-ferroelectric phase transition. Transition temperature values depend on the R ion type and are lower than in pure lead titanate by 80-100 K. A broad anomaly of dielectric permittivity is found below 140-180 K, where magnetization also increases due to the quadratic magnetoelectric coupling between ferroelectric and magnetic states. For the (Pb_(0.845)Sm_(0.08)Fe_(0.035))(Ti_(0.98)Mn_(0.02))O_3 composition, the piezoelectric charge coefficient at room temperature was d_(31) ～-6.5 pC/N and the remanent magnetization M_r at room temperature was about 0.1 emu/g.