Single phase multiferroic compounds by doping Bi4Ti3O12 with Fe+3 ions

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08-081 Marcelo Stachiotti Stachiotti, M.(Instituto de Fisica Rosario); Lavado, C.(Instituto de Fisica Rosario); Rebola, A.(Instituto de Fisica Rosario); The effects of Fe doping on electric and magnetic properties of Bi4Ti3O12 (BIT) were investigated. BIT is one of the simplest compounds in the Aurivillius family with a vast potential for applications, specially as NvRAMs. We developed multiferroic compounds by Fe3+/Nb5+ co-substitution on Ti4+ sites. In this way Bi4Ti3-x(Nb0.5Fe0.5)xO12 ceramics were synthesized by a solid state reaction technique. We show that the structure of the compounds with x ? 1 is the characteristic one of the n=3 member of the Aurivillius family. A secondary pyrochlore phase was detected for x > 1, and this phase is dominant at x=2. We show that the Aurivillius x=2 phase can be stabilized however by the addition of La (Bi3.25La0.75TiNbFeO12 ,for example). 
Raman measurements corroborated that both Fe3+ and Nb5+ 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 Fe3+ ions. The results are corroborated by first-principles calculations on Bi4TiNbFeO12, which predict an electric polarization of ~35 uC/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.
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