Single phase multiferroic compounds by doping ferroelectrics with magnetic ions

BAROLIN, SEBASTIAN; LAVADO, CRISTIAN; STACHIOTTI, MARCELO; REBOLA, ALEJANDRO; PELLEGRI, NORA; IMHOFF, LUCIA

Buenos Aires

Workshop; Multifunctional Oxides: Science and Synergy between fundamental novel technologies; 2017

In this talk I present the effects of Fe doping on electric and magnetic properties of two ferroelectric oxides: Bi4Ti3O12 (BIT) and PbZr0.52Ti0.48O3 (PZT). BIT is one of the simplest compounds in the Aurivillius family with a vast potential for applications, specially as NvRAMs. PZT is the dominant ferroelectric material for practicalapplications because of its large piezoelectric constant and large remnant polarization. To ensure charge neutrality, the strategy is to develop multiferroics from those oxides by Fe3+/Nb5+ co-substitution on (Ti-Zr)4+ sites. For that purpose, Bi4Ti3-x(Nb0.5Fe0.5)xO12ceramics were synthesized and we show that the structure for the compounds with x ≤ 1 is the characteristic one of the n=3 member of the Aurivillius family. Raman measurements corroborated that both Fe3+ and Nb 5+ ions are incorporated into the Ti sites. Dielectric studies at room-temperature displayed the reduction of dielectric constant and loss tangent with substitution, while the switching behavior shows ferroelectric character.Magnetic measurements indicated antiferromagnetic spin correlations between Fe 3+ ions. The results are corroborated by first-principles calculations on Bi4TiNbFeO12, which predict an electric polarization of ~30uC/cm2 and confirm the antiferromagnetic ground state, for which we obtain a nearest-neighbor super-exchange coupling J=7meV. We assessed different B sites configurations and found a preference for Fe3+ ions to be located at the outer perovskite B sites. For the case of PZT, [PbFe0.5Nb0.5O3]0.5 [PbZr0.52Ti 0.48O3]0.5 thin films were fabricated by a chemical solution deposition technique. The films were prepared by spin‐coating on Pt/TiOx/SiO 2/Si substrates and thermally treated by rapid thermal annealing. We observed the coexistence of ferroelectric and ferromagnetic properties at room temperature, similar to what was reported in bulk ceramics.