**4.3 Magnetoelectric coupling**

Magnetoelectric bonding (ME), which can detect coexistence with the same combination of ferroelectric and magnetic properties, maybe the most notable feature of nano-BFO-based materials. As a result, many researchers are focusing on the promise of merging the boundaries of magnetic and electrical order. Zhao et al. [3] were the first to demonstrate the electrical control of the antiferromagnetic domain structure in a single-phase BFO film, showing a solid interaction between the two types of structure at room temperature. They found that before and after electric cooling, the antiferromagnetic base structure was firmly attached to the ferroelectric base structure. Automatic polarization occurs near the axis. The angles 71o , 109o , and 180o show three distinct divisions as the rhombohedral axis changes. It was found that the interaction between the antiferromagnetic domain and the ferroelectric domains occurs only with a polarization of 71o and 109o , but not with a change of 180o ferroelectric polarization. This work is an essential first step for researchers interested in investigating ME nano-BFO compound materials. However, due to the slight spin canting, it is not easy to achieve the significant coefficient of magnetoelectric coupling magnetization. The acquisition of magnetic anisotropy in the optical connector of ferromagnetic-antiferromagnetic heterostructures allows for a more extraordinary animation of device applications. Thin-film heterostructures also benefit from the way magnetic anisotropy of the system can be constructed with epitaxy. As a result, researchers are keenly interested in combining ferromagnet-multiferroic exchange heterostructures for BFO sub-film, particularly oxide ferromagnet/ BFO heterostructures and transition metal ferromagnet/BFO heterostructures. For oxide ferromagnet/BFO heterostructures, La0.7Sr0.3MnO3 (LSMO) is popular. It is found that different magnetic exchange effects were produced at different LSMO/ BFO sites because Fe3+ and Mn3+ or Mn4+ are ferromagnetic, competing with a wide range of antiferromagnetic order. Later, Wu et al. [19] used the LSMO/BFO system

to demonstrate the electronic control of exchange bias. They found a reversible shift between the two biased regions by changing the ferroelectric polarization of the BFO. This is a significant step forward in controlling pornography by power control, and it is an essential step towards spintronic electronic control devices. However, due to the relative temperature dependence of the ferromagnet/BFO heterostructure exchange, achieving renewable electrical control of the magnetoelectric junction at room temperature remains difficult. The ferromagnet transition metal (Co0.9Fe0.1) ferromagnetic layer to form a heterojunction with the BFO to control the local magnetic field room temperature. Magnetic anisotropy was modified using an electric field in the aircraft. After an electrical switch was investigated, they found that the linear domains moved from left to right. The domains then recede after the use of a different electric field. At room temperature, the electric field can control the flexible wall of the electric field, as shown in this series of pictures. Most importantly, this work demonstrated the magnetoelectric in front of the electric field at room temperature.
