First-principle Studies On Magnetic Properties Of Defect-engineered Rutile SnO₂

Spintronics could organically combine the two properties of electron spin and charge,which has broad application prospects in the fields of integrated circuits and quantum computers and is a hot spot in international research.Diluted magnetic semiconductors(DMSs)are the most promising materials for spintronic devices.SnO₂ is considered to be one of the most promising DMSs.Therefore,SnO₂ DMSs have attracted a lot of attention,but the related research is still in an exploratory stage.The origin of dilute magnetic semiconductor magnetism has not yet been fully understood.In this paper,the electronic structure and magnetic properties of intrinsic SnO₂,Co-only doped,and Co+M(M=Ta,Nb,Li)co-doped SnO₂ are studied by the first-principles calculation method based on density functional theory and SnO₂ as the research object.The effect of doping on the electronic structure and magnetic properties of SnO₂ are analyzed.This paper first studies the electronic structure and magnetic properties of intrinsic and Co-doped SnO₂ and confirms that intrinsic SnO₂ is a non-magnetic semiconductor.In the Co-doped SnO₂ system with a doping concentration of 4.2%,two Co atoms will make the system have a magnetic moment of 1.84,Co will form clusters,and the system will be ferromagnetic.The magnetic moment is mainly distributed on the Co element.The 3d orbital of Co will hybridize with the 2p orbital of the O,resulting in the non-magnetic O being induced to be magnetic.After Co doping,the system changes from semiconductor to semi-metallic.At the same time,considering the O vacancy defect,through the calculation of the formation energy,it is found that O vacancy is easier to form in the Co-only doped SnO₂ system.Studies have shown that the introduction of O vacancies greatly increases the atomic magnetic moment of Co,from 0.74?_B without O vacancies to 2.74?_B.This is because the introduction of O vacancies increases the 3d orbital lone pair electrons of Co and inhibits the superexchange effect.The double exchange effect changes the system from ferromagnetic to antiferromagnetic.At the same time,the existence of O vacancies changes the system from semi-metallic to metallic.In addition to the Co-only doped SnO₂,the electronic structure and magnetic properties of Co-Ta,Co-Nb,and Co-Li co-doped SnO₂ systems are also studied.In the presence of O vacancies,the Co-Ta co-doped system with a doping concentration of 12.5%exhibits antiferromagnetism.When Ta doping is introduced into the SnO₂ system,the magnetic moment of Co in the system decreases slightly,from 2.74to 2.54,There is no magnetic moment in Ta itself and has little effect on the magnetic properties of the system.The Co-Nb co-doped system with a doping concentration of 12.5%exhibits ferromagnetism.Although the introduction of Nb also causes a slight decrease in the magnetic moment of Co,it also changes the spin direction of Co.Nb introduces a different magnetic field.The acting force transforms the system from anti-ferromagnetism to ferromagnetism,which has a great influence on the magnetism of the system.In the absence of O vacancies,the Co-Li co-doped system with a doping concentration of 6.25%exhibits ferromagnetism and increases the magnetic properties of the system.This is because the magnetic moment of Co increases from 0.7to 0.935due to the addition of Li.Moreover,the addition of Li also strengthens the orbital hybridization between the 3d electrons of Co and the 2p electrons of O.The co-doping of different elements makes the SnO₂ system exhibit rich magnetic properties,which provides an effective way to tune the magnetic properties of SnO₂ diluted magnetic semiconductors.