Hybrid antiferroelectric-ferroelectric domain walls in noncollinear antipolar oxides

Antiferroelectrics are emerging as advanced functional materials with unique electric properties enabled by the antipolar arrangement of their electric dipoles. Additional functionalities and novel physical nanoscale phenomena are expected in systems with noncollinear antipolar dipole structures. Here we demonstrate how the onset of antiferroelectricity in K₃[Nb₃O₆∣(BO₃)₂] drives noncollinear ordering of electric dipole moments, which leads to unusual hybridization of antiferroelectric and ferroelectric responses. Besides the double-hysteresis loop common to antiferroelectrics, a pronounced piezoresponse and electrically switchable hybrid domains are observed using scanning probe microscopy. Scanning transmission electron microscopy shows that the domains are separated by atomically sharp and micrometre-long charged domain walls with inseparably entangled discontinuities in the antiferroelectric and ferroelectric orders. Hybrid antiferroelectric-ferroelectric responses are expected in a wide range of noncollinear systems.