RESUMO
Two-dimensional (2D) nanosheet arrays with unidirectional orientations are of great significance for synthesizing wafer-scale single crystals. Although great efforts have been devoted, the growth of atomically thin magnetic nanosheet arrays and single crystals is still unaddressed. Here we design an interisland-distance-mediated chemical vapor deposition strategy to synthesize centimeter-scale atomically thin Fe3O4 arrays with unidirectional orientations on mica. The unidirectional alignment of nearly all the Fe3O4 nanosheets is driven by a dual-coupling-guided growth mechanism. The Fe3O4/mica interlayer interaction induces two preferred antiparallel orientations, whereas the interisland interaction of Fe3O4 breaks the energy degeneracy of antiparallel orientations. The room-temperature long-range ferrimagnetic order and thickness-tunable magnetic domain evolution are uncovered in atomically thin Fe3O4. This strategy to tune the orientations of nanosheets through the an interisland interaction can guide the synthesis of other 2D transition-metal oxides, thereby laying a solid foundation for future spintronic device applications at the integration level.
RESUMO
2D multiferroics with magnetoelectric coupling combine the magnetic order and electric polarization in a single phase, providing a cornerstone for constructing high-density information storages and low-energy-consumption spintronic devices. The strong interactions between various order parameters are crucial for realizing such multifunctional applications, nevertheless, this criterion is rarely met in classical 2D materials at room-temperature. Here an ingenious space-confined chemical vapor deposition strategy is designed to synthesize atomically thin non-layered ε-Fe2 O3 single crystals and disclose the room-temperature long-range ferrimagnetic order. Interestingly, the strong ferroelectricity and its switching behavior are unambiguously discovered in atomically thin ε-Fe2 O3 , accompanied with an anomalous thickness-dependent coercive voltage. More significantly, the robust room-temperature magnetoelectric coupling is uncovered by controlling the magnetism with electric field and verifies the multiferroic feature of atomically thin ε-Fe2 O3 . This work not only represents a substantial leap in terms of the controllable synthesis of 2D multiferroics with robust magnetoelectric coupling, but also provides a crucial step toward the practical applications in low-energy-consumption electric-writing/magnetic-reading devices.
RESUMO
The control of magnetism by electric means in single-phase multiferroic materials is highly desirable for the realization of next-generation magnetoelectric (ME) multifunctional devices. Nevertheless, most of these materials reveal either low working temperature or antiferromagnetic nature, which severely limits the practical applications. Herein, we selected room-temperature multiferroic Ga0.6Fe1.4O3 (GFO) with ferrimagnetism to study electric-field-induced nanoscale magnetic domain reversal. The GFO thin film fabricated on the (111)-orientated Nb-doped SrTiO3 single-crystal substrate was obtained through the pulsed laser deposition method. The test results indicate that the thin film not only exhibits ferroelectricity but also ferrimagnetism at room temperature. More importantly, reversible and nonvolatile nanoscale magnetic domains reversal under pure electrical fields is further demonstrated by taking advantage of its ME coupling effect with dependent origins based on iron ions. When providing an appropriate applied voltage, clear magnetic domain structures with large size can be easily manipulated. Meanwhile, the change ratio of the electrically induced magnetizations in the defined areas can reach up to 72%. These considerable merits of the GFO thin film may provide a huge potential in the ME multifunctional devices, such as the multi-value, low-energy-consuming, and nonvolatile memory and beyond.