Theoretical Design And Properties Of Two-dimensional Intrinsic Magnetic Materials

Spintronics that employs the spin of electrons to complement or replace charge has widespread applications in the future information technology,due to its great promise with superior characteristics of low energy consumption,fast processing speed,and high integration density,which has attracted general attention in the science world over the past decade.Since 2004,the discovery of graphene has triggered enormous efforts for exploration of new two-dimensional(2D)materials with fantastic physicochemical properties.As the increasing microelectronics,devices will be smaller,more integrated and more efficient,which means that the age of only manipulating charge is fading and the multi-degree-of-freedom materials will flourish.Particularly,2D ferromagnets are considered as the key to achieve the goals of future microelectronics with the perfect dual attributes of charge and spin,among which magnetic half-metals and semiconductors have been also widely regarded as the important candidates for the applications of spintronics.At present,there are still many challenges to accurately inject magnetism into non-magnetic materials.The development of new 2D intrinsic ferromagnets is imminent.As the improvement of density functional theory and the rise of computer science,it has become the normalcy to design functional materials theoretically to guide experimental synthesis.So,On the theoretical level,this paper has refined two new two-dimensional intrinsic ferromagnetic materials.One of them is a magnetic half-metal and the other is a magnetic semiconductor.Moreover,both of them possess robust ferromagnetism,large magnetic anisotropy and relatively high Curie temperatures.These 2D materials with excellent electromagnetic properties provide theoretical support for the potential applications of future room temperature spintronics.(1)Electromagnetic properties of ferromagnetic half-metal hexagonal manganese carbideWe predict from first-principles calculations that the 2D pristine hexagonal manganese carbide(h-MnC)monolayer exhibits robust ferromagnetism and half-metallic features with 100%spin polarization around the Fermi level,considerable magnetic anisotropy energy and wide half-metallic gap.We confirm the robustness of the ferromagnetism and half-metallicity against the external strain from-6%to 10%.Employing the Monte Carlo simulations with Heisenberg model,the estimated Curie temperatures within the realistic strain range are around 200 K.Also,some feasible experimental fabrication routes are proposed to realize this sheet by heterostructure engineering and exfoliation techniques with MX2(M=Mo,W;X=S,Se,Te)substrates.In summary,the robustness of the half-metallicity in combination with the high temperature ferromagnetism render the freestanding h-MnC monolayer a promising materials for practical spintronic nanodevices.(2)Electromagnetic properties of ferromagnetic semiconductor hexagonal chromium carbideWe identify the stable existence of the hexagonal chromium carbide(h-CrC)sheet.As a ferromagnetic semiconductor,it has a narrow band gap of 0.32 eV and possesses an ultra-high electron mobility of the order of 104.Additionally,apart from having a large magnetic anisotropy with a out-of-plane easy magnetization axis,it also has a Curie temperature of up to 555 K based on the Monte Carlo simulation of classic Heisenberg model,which is much higher than the room temperature.Moreover,the robust semiconducting and ferromagnetic properties will be more excellent under biaxial tensile strain.Additionally,the appropriate compression strain not only causes the h-CrC semiconductor sheet to become half-metal,but also significantly increases the Curie temperature and magnetic anisotropy energy.On the other hand,at the tensile strain of 5%,the indirect to direct band gap transformation of h-CrC monolayer began to take place.Finally,we proposed a feasible synthesis route for the deposition of h-CrC monollayer film on MoS2 monolayer substrate.All of these studies show that the h-CrC monolayer has a wide range of future applications in future nanoelectronics and spintronics.