Ceramic ${\text{Bi}}_{1-x}{\text{Nd}}_x{\text{FeO}}_3$ solid solutions in the approximate compositional range $0.15\le x\le 0.25$ undergo first-order antiferroelectric $\left(\text{AFE}\right)\leftrightarrow \text{paraelectric}$ (PE) phase transitions between $300°\text{C}$ and room temperature. The orthorhombic AFE ($Pnam$, $\surd 2a_{\text{c}}\times 2\surd 2a_{\text{c}}\times 4a_{\text{c}}$, where $a_{\text{c}}\approx 4\text{Å}$ and is the lattice parameter of an ideal cubic perovskite) and PE ($Pbnm$, $\surd 2a_{\text{c}}\times \surd 2a_{\text{c}}\times 2a_{\text{c}}$) structures differ not only in the type of octahedral tilt system but also in the pattern of $A$-cation (Bi/Nd) displacements. The $\text{AFE}\leftrightarrow \text{PE}$ transition is accompanied by a large $\left(\approx 2\mathrm{\%}\right)$ discontinuous volume change similar to that observed at the ferroelectric $\left(\text{FE}\right)\leftrightarrow \text{PE}$ transition in ${\text{BiFeO}}_3$. For all compositions, the structural transition occurs within the $G$-type antiferromagnetic (AFM) state. Variable-temperature magnetic measurements reveal a strong coupling between the $\text{AFE}\leftrightarrow \text{PE}$ transition and the magnetic ordering. Rietveld refinements using neutron powder-diffraction data demonstrate that the structural transition is accompanied by reorientation of magnetic dipoles within the $G$-type AFM array resulting in a significant increase in magnetization.

• Received 6 November 2009

DOI:https://doi.org/10.1103/PhysRevB.81.020103