Study On Spin Transport Properties Of Two-dimensional Magnetic Materials YN₂ And VS₂

Two-dimensional graphene-like materials have potential applications in electronics and electrochemistry due to the advantages of extraordinary physical and chemical properties,ultrathin thickness and facile synthesis.However,most of the pristine graphene-like two-dimensional materials are non-magnetic,and the emergence of magnetism usually needs an external electric field,substrate,strain,vacancy,or doping,which is not easily controlled in an experiment,limiting the potential applications in spintronics.Recently,researchers found two two-dimensional graphene-like materials with intrinsic ferromagnetism,which are ferromagnetic half-metallic YN₂ monolayer and ferromagnetic semiconductor VS₂ nanosheets.To explore the possible spintronic and thermal spintronic applications,herein,we designed spintronic and thermal spintronic devices based on the two-dimensional YN₂ and VS₂,and their spin transport properties are studied by using the first-principles combined with nonequilibrium Green's function method.We found that the devices based on the YN₂ monolayer exhibit perfect dual spin filtering effect and dual spin diode effect when a bias voltage is applied.Moreover,the devices also exhibit spin-polarized electric currents in different direction under a temperature gradient,i.e.,excellent spin Seebeck effect.We also analyze the density of states of the electrodes and investigate the contribution of atomic orbitals to electronic transport.For the devices based on VS₂ monolayer,they also show better spin Seebeck effect,and the thermally induced spin filtering effect and negative differential resistance effect.We also find that the thermal magnetoresistance is as high as 1.1×10⁵%.The current spectrums of the devices based on VS₂ monolayer are presented to explain the variation of the spin-resolved current induced by the temperature difference.The corresponding mechanisms of these peculiar effects in these devices based on the YN₂ and VS₂monolayers can be explained by the calculated spin-resolved band structure and transmission spectrum.From these theoretical calculations and analysis,we predict the potential applications in spintronics and thermal spintronics for the ferromagnetic half-metallic YN₂ monolayer and the ferromagnetic semiconductor VS₂ monolayer,which will be helpful to explore the transport properties based on other similar two-dimensional magnetic materials.