Advanced materials: enhancement of coercive field and Curie temperature caused by neighbor effect in van der Waals heterojunction
two-dimensional magnetic materials have attracted extensive attention because of their important applications in spintronics magnetic storage. Since the discovery of intrinsic two-dimensional ferromagnetism in cri3 cr2ge2te6 crystals with atomic layer thickness in 2017 a variety of two-dimensional ferromagnetic materials have been discovered. However the critical temperature of the intrinsic two-dimensional ferromagnetic materials is generally very low so how to improve the Curie temperature of the existing two-dimensional magnetic materials is very important for its application in magnetic memory devices. As a kind of itinerant ferromagnet fe3gete2 has large magnetic anisotropy high Curie temperature relatively stable characteristics. It is a kind of two-dimensional material with potential to realize room temperature ferromagnetism. At present the magnetism of two-dimensional materials can be controlled by applying external fields (such as electric field stress pressure etc.) but compared with the external field control the ferromagnetic / antiferromagnetic interface proximity effect control is an effective way without additional energy consumption.
Han Junbo researcher of National Center for pulsed high magnetic field of Huazhong University of science technology ye radium associate researcher of School of optoelectronic information systematically studied the magnetic properties of mechanically exfoliated two-dimensional feps3 fe3gete2 crystals their heterojunction by using pulsed field magnetization measurement technology micro magneto-optical Kerr measurement technology. The results show that the two-layer antiferromagnetic / ferromagnetic heterojunction the three-layer antiferromagnetic / ferromagnetic / antiferromagnetic heterojunction exhibit exchange bias due to the nearest neighbor coupling effect. The coercivity field of the two-layer three-layer antiferromagnetic / ferromagnetic / antiferromagnetic heterojunction is more than double that of the pure fe3gete2 the Curie temperature is increased by about 30 K the magneto-optical Kerr angle is also increased significantly. In order to determine the coupling mechanism between FPS FGT we further analyzed the domain characteristics of FGT FPS / FGT. When FPS FGT are coupled together a variety of magnetic states exchange biases will occur the spin structure in FGT will be significantly affected by FPS through proximity coupling. For the three-layer structure the exchange bias is more obvious than FPS / FGT due to the double interface thicker FPS layer in FPS / FGT / FPS.
this study shows that the ferromagnetic / antiferromagnetic nearest neighbor coupling effect can effectively control the magnetic properties of two-dimensional materials which not only provides a simple effective method to control the TC of two-dimensional ferromagnetic materials but also provides people with an understing Revelation of two-dimensional properties The proximity coupling between FM AFM provides a platform for the future development of room temperature spintronic devices based on two-dimensional magnetic materials.
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