Dielectric and Magnetic Properties of Ta2O5-doped PrFeO3–PbTiO3 and PrFeO3–BiFeO3 Ceramics

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Polarization-electric field ($P$–$E$) and magnetization-magnetic field ($M$–$H$) hysteresis curves have been characterized in the solid solutions of ($1-x$)PrFeO3–$x$PbTiO3+$y$Ta2O5 ($y=0--0.015$ mole) and 0.2PrFeO3–0.8BiFeO3. Neutron and X-ray diffraction data were collected for crystal structural analysis. The ($1-x$)PrFeO3–$x$PbTiO3 were ferromagnetic at $0.2<x<0.7$. Remanent magnetization $M_{\text{r}}$ decreased from 0.09 emu/g at $x=0.4$ to 0.02 emu/g at $x=0.65$. The $P$–$E$ curve measurements showed that the solid solution was paraelectric at $x=0.4$. The shape of the $P$–$E$ curve showed a more ferroelectric nature at $x=0.65$. Remanent polarization $P_{\text{r}}$ was 0.8 μC/cm2 at $x=0.65$. The Rietveld refinement of neutron data showed a structural transition occuring at $x\geq 0.7$ from Pbnm ($a=5.552$, $b=5.540$ Å, $c=7.833$ Å) to I4cm ($a=b=5.54$ Å, $c=7.841$ Å) The structural analysis indicates that the solid solutions are ferroelectric only at $x>0.6$. The 0.2PrFeO3–0.8BiFeO3 showed a spontaneous magnetization of 0.3 emu/g at room temperature and remanent polarization $P_{\text{r}}$ of 0.6 μC/cm2. Addition of Ta2O5 substantially changed the magnetic properties. The antiferromagnetic ordering is considered not to have a direct relationship with the weak ferromagnetism observed in this system.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2003-04-15