Novel multiferroic (Pb1 − 3x/2Ndx)(Ti0.98 − yFeyMn0.02)O3 ceramics with coexisting ferroelectricity and ferromagnetism at ambient temperature

Abstract

We report the evolution of structural, dielectric, ferroelectric and ferromagnetic properties in novel (Pb1−3x/2Ndx)(Ti0.98−yFeyMn0.02)O3 perovskite ceramics(x=0.08, 0<y<0.05). We found room-temperature ferroelectric polarization and ferromagnetism for higher amount of iron ions(y≥0.04). The paraelectric-ferroelectric phase transition occurred between 650 and 670K for 0≤y≤0.05. Ferromagnetic hysteresis was measured at different temperatures on samples with y≥0.04. Detailed structural analysis evidenced the variation of unit cell parameters with y increasing, confirming the substitution of the iron element in the lattice. 57Fe Mössbauer spectroscopy evidenced that iron ions occupy Ti positions in the perovskite lattice, with the oxidation state Fe3+ and two coordination types. X-ray photoelectron spectroscopy confirmed the presence of iron only as Fe3+ and, moreover, evidenced the presence of a substantial amount of Ti3+ ions in the structure. The presence of both Fe3+ (spin 5/2) in different coordinations as well as Ti3+ (spin 1/2) magnetic ions in B-site positions drives the occurrence of magnetic properties from low temperature to above room temperature, through superexchange Fe3+-O-Fe3+, Fe3+-O-Ti3+ and Ti3+-O-Ti3+ interactions. The finding of coexistent ferroelectric and ferromagnetic properties in these compounds ground the route to facile synthesis of multiferroics by simply doping a classical perovskite ferroelectric material like PbTiO3 with an adequate amount of transition magnetic ions.