Magnetoelectric control of spin-chiral ferroelectric domains in a triangular lattice antiferromagnet

We have grown single crystals of a triangular lattice antiferromagnet (TLA), ${\text{CuCrO}}_2$, and investigated the correlation between magnetic and dielectric properties. Two magnetic phase transitions are observed at $T_{\text{N}2}\approx 24.2\text{K}$ and $T_{\text{N}1}\approx 23.6\text{K}$. It was found that ferroelectric polarization along the triangular lattice plane develops at $T_{\text{N}1}$, suggesting that the system undergoes a transition into an out-of-plane $120°$ spin-chiral phase at $T_{\text{N}1}$. The TLA provides an opportunity for unique magnetoelectric control of spin-chiral ferroelectric domain structures by means of electric and/or magnetic fields.

Figure 1

(Color online) (a) Temperature profiles of ${\chi }_c$ (gray line) and ${\chi }_{ab}$ (black line) for a single crystal of ${\text{CuCrO}}_2$. (b) $P_{ab}$ versus electric field at selected temperatures. Inset of (a): crystal structure of ${\text{CuCrO}}_2$.

Figure 2

(Color online) Temperature profiles of (a) ${\chi }_c$ (gray closed circles) and ${\chi }_{ab}$ (black open circles), (b) $C$, (c) ${\epsilon }_c$ (gray line) and ${\epsilon }_{ab}$ (black line) at 1 kHz, and (d) $P_c$ (gray line) and $P_{ab}$ (black line). Measurement of $P_c$ and $P_{ab}$ in (d) were performed with (ON) or without (OFF) electric field of 400 kV/m after poling the crystal. (e) The (001) projection of ${\text{Cr}}^{3+}$ trigonal layer and symmetry operations (2, $m$, and $\overline{3}$) in ${\text{CuCrO}}_2$. (f), (g) Spin configurations with the remained symmetry operation in the case of the spiral plane parallel to the (110) and the $\left(1\overline{1}0\right)$ planes, respectively. Gray (light gray) and orange (dark gray) planes denote the spiral plane and the $m^{\prime }$ plane, respectively.

Figure 3

(Color online) Temperature profiles of $P_{ab}\left(\text{ON}\right)$ at selected magnetic fields (a) $H_{ab}\parallel P_{ab}$, (b) $H_{ab}\perp P_{ab}$, and (c) $H_c\perp P_{ab}$ for a single crystal of ${\text{CuCrO}}_2$. (d)–(h) Schematic illustrations of ferroelectric domain configurations in various types of external fields in the situation where the (110) spiral plane is realized and electrodes are deposited onto the (110) plane. Thick arrows denote the directions of $P$ of the respective existing ferroelectric domains. The size of arrows schematically corresponds to the volume of each ferroelectric domain.