Spin-driven ferroelectricity in the delafossite CuFe1−xRhxO2 (0≤x≤0.15)

The effect of substitution at the Fe site in the CuFeO2 delafossite is known to induce a magnetic structure responsible for the appearance of electric polarization. A CuFe1−xRhxO2 series of ceramic samples is studied in order to determine the composition range exhibiting such a polar state. It is found that for the CuFe1−xRhxO2 (x≤0.15) solid solution, the Néel temperature TN2 decreases monotonously with x from 11.5 K to 5.9 K, for x=0.00 to 0.15, respectively, and that the dielectric peak and the polarization transition temperatures coincide with TN2. In contrast, the dielectric peak and polarization magnitudes go through an optimum for CuFe0.92Rh0.08O2 (x=0.08). These results demonstrate that, compared to other substituting elements, the Rh3+ for Fe3+ substitution in CuFeO2 allows to extend significantly the ferroelectric region in the (x, T) phase diagram in connection with the slower TN2 decrease.

Graphical AbstractPolycrystalline samples of the delafossite solid solution CuFe1−xRhxO2 were synthesized and characterized. Polarization has been observed in the range 0.02