Magnetoelectric hysteresis loops in Cr${}_2$O${}_3$ at room temperature

We revisit the room-temperature linear magnetoelectric effect in Cr${}_2$O${}_3$ single crystals. It was found that the temperature dependence of dielectric constants in a magnetic field $H$ shows a λ-shaped peak at the Néel temperature (≈307 K) and that electric polarization induced by applying $H$ is reversed with a hysteresis by sweeping an electric field $E$. Similar reversal and hysteretic behaviors were also observed in the $H$ dependence of magnetization induced by applying $E$. These results imply that Cr${}_2$O${}_3$ behaves as a typical ferroelectric (ferromagnet) in finite $H$ ($E$) even at room temperature. We discuss the ferroic behaviors observed in the linear magnetoelectric system in the context of recent studies on multiferroics.