Room-temperature ferroelectricity in magnetically ordered CoH2SeO4 flakes

Here, we demonstrate the existence of magnetic ordering and sliding ferroelectricity in two-dimensional CoH2SeO4 multilayers. The experimental result reveals the antiferromagnetic order in powder sample, and first-principles calculation indicates the antiferromagnetic ground state with T-N approximate to 75 K in CoH2SeO4 single layer. The sliding ferroelectricity with an asymmetric triplet potential well is theoretically predicted and experimentally confirmed by 180 degrees-piezoelectric hysteresis loops, switchable domains and second harmonic generation signals in CoH2SeO4 multilayers. The vertically stacked ferroelectric capacitor shows both polarization and capacitance hysteresis loops. A ferroelectric transition temperature of similar to 370 K is obtained from the temperature-dependent dielectricity. The emergence of sliding ferroelectricity and anti-ferromagnetism points out a new route for obtaining low-dimensional multiferroic materials.