Real-Time Imaging of Nonequilibrium Domain Evolution into a Multiferroic Phase

The properties and functionalities of multiferroic materials are governed by the microscopic domain structures of coexisting ferroic orders and their mutual coupling. Active control over multiferroic domains via external stimuli is desirable, with prominent examples in magnetoelectric inversion or transfer of domain patterns. These approaches typically harness electric or magnetic fields to affect the thermodynamically stable domain configuration within a multiferroic phase. Optical or thermal quenches through phase transitions can be used to transfer structural features between distinct phases, creating novel and potentially functional domain structures unattainable in thermal equilibrium. The impact of such transitions on multiferroic domain patterns and their dynamic evolution, however, remains a largely open subject.<br/><br/>In this work, we combine real-time Faraday imaging at kHz frame rates with fast optical excitations to investigate the evolution of domains across spin-reorientation transitions and into the multiferroic phase of Dy_0.7Tb_0.3FeO₃. We find that optically-induced thermal quenches of the system can be harnessed to imprint the characteristic bubble domain pattern of the weak ferromagnetic order at elevated temperatures onto the low-temperature multiferroic phase. We identify the quenching rate across the different spin reorientation transitions as the decisive parameter governing the domain memory and the formation of metastable domain states forbidden under equilibrium conditions. Our results highlight the potential of optical stimuli for the switching and control of multiferroic domain structures, enabling the creation of new functional states via nonequilibrium pathways.