Observation and Control of Nano-Domains in Improper Ferroelectric Gd₂(MoO₄)₃

In improper ferroelectrics, spontaneous polarization arises as a biproduct of magnetic or structural instabilities. The important difference from proper ferroelectrics is that the primary order parameter is not the electric polarization, and this difference promotes the natural formation of a plethora of different types of functional domains and domain walls. Gd₂(MoO₄)₃ is a classical example of an improper ferroelectric material and has been intensively studied with respect to its ferroic properties, which govern the ferroelectric/ferroelastic domain structure.<br/><br/>In this work, we expand previous optical investigations to the nanoscale. Using Piezoresponse Force Microscopy, we image the pattern of ferroelectric and anti-phase domains in Gd₂(MoO₄)₃. In addition to the established domain structures, we resolve so far unexplored stripe-like nano-domains with a periodicity of about 60 nm. We demonstrate reversible switching of these nano-domains by local electric fields and their control by application of mechanical stresses. Our findings provide new insight into the physics of Gd₂(MoO₄)₃ at the level of the domains and domain walls, and introduce novel opportunities for property engineering of this model system at the local scale.