An international team of researchers created ultra-thin ferromagnetic materials that may become the basis for new spintronic devices. Scientists had based two-dimensional sulphide of tantalum and created on its basis a two-layer structure with ferromagnetic properties. For this purpose the authors introduce atoms of different transition metals between layers of sulfide. About the methodology the researchers said in an article published in the journal Nature.
In spintronic devices, in contrast to the usual electronic, the role of the media does not the electron charge and its spin. A spin-current can be used for information transfer and energy storage. Logic circuits based on spintronics perform operations faster electronic, emit less heat and are resistant to ionizing radiation.
To create such devices offered quite a lot of different compounds and one of the most promising classes — two-dimensional materials. Recently, they are attracting increasing interest among scientists due to their electrical, mechanical and magnetic properties. Modification of these materials with atoms of heavy metals can significantly improve their properties — for example, to make a compound superconductor or termoelectrica. Also introducing metal atoms into the structure of the two-dimensional material can change its magnetic properties: for example, made of diamagnetic ferromagnetic. It is the combination of small thickness and magnetic order such two-dimensional materials and makes them suitable for use in spintronic devices.
To embed (interkaliruet) in the two-dimensional structure of the material atoms of another element in several ways. The most commonly used method is to increase the two-dimensional layer on the surface of a solid substrate from the gas or liquid phase which contains molecules of the primary connection and interkaliruet. But with this method the yield of the target material is low, and the reproducibility of results is poor. The alternative modification is introduction of metal atoms into the space between the layers of material are bound together by weak van der Waals interactions. However, at the moment this method allows you to interkaliruet two-dimensional material atoms only some of the alkaline, transition and noble metals and small organic molecules.
An international group of scientists under the leadership of Professor Kian Ping Loh (Loh Kian Ping) from the National University of Singapore have found a way to expand the capabilities of this method. They were able to interkaliruet sulfide of tantalum TaS2 atoms of tantalum and other transition elements and learned to control material properties by changing the metal content of the target compound. For this, the researchers used the method of molecular beam epitaxy. With the help of it the researchers first applied to the silicon substrate atomically thin layer of sulfide, and then on top of it slowly sprayed atoms of a transition element. Then followed by a second layer of sulphide, which covered the metal atoms. The researchers thus got a structure of two layers of two-dimensional materials. Changing the amount of metal in the interlayer space the researchers were able to vary the physical properties of the resulting material.