Theoretical Study On The Mechanism Of Spinterface States Formation

In molecular spintronics,the atomic-scale controllable interface between the electrode and the molecule is called spinterface.The specially designed spinterface can control the spin injection from electrode to molecule.Based on the first-principles calculation of density functional theory,this thesis discusses the formation mechanism of hybrid interface states at the spin interface,and studies the effects of interactions between several typical molecules and different ferromagnetic electrode surfaces,as well as the properties of interface states between molecules and oxidized electrode surfaces.The main research contents are as follows:At present,most studies on the hybridized interface states of the interaction between molecules and ferromagnetic metals believe that the hybridized interface states are contributed by the coupling of the out-of-plane orbital?? orbital?of molecules and the orbital of metals,that is,the influence of the in-plane orbital?? orbital?of molecules on the hybridized interface states is not taken into account.Until 2016,an experimental group,using spin-resolved photoemission spectroscopy measurements,demonstrated that alkanes with only ? bonds can form highly spin-polarized hybridized interface states when they are adsorbed on ferromagnetic metals,which directly demonstrated the importance of studying molecules' in-plane orbitals.Therefore,combined with existing experimental results,we analyzed the structures of pentane?C₅H₁2?,1,10-phenanthroline?C₁2N₂H₈?and fullerene C60 adsorbed on the surfaces of bcc-Fe?001?and fcc-Co?111?.The results show that highly spin-polarized interface states can be generated when the molecule is adsorbed on the surface of ferromagnetic substrates,no matter whether the molecule contains out-of-plane ? bonds or not.However,compared with molecules with no ? bonds,molecules with ? bonds have stronger interaction with ferromagnetic substrates and have greater influence on the magnetic moment change of ferromagnetic surfaces.At the same time,for molecules with both? and ? bonds,the influence of ? bonds on the hybrid interface state of the whole adsorption structure is significant.In order to study the properties of the interface state when molecules are weakly adsorbed on the ferromagnetic substrate surface,we analyzed the structure of molecule on oxidized electrode surfaces,that is,the structure of the C₁2N₂H₈ molecule adsorbed on the oxidized Fe?001?and Co?111?surfaces.The ferromagnetic substrate surface is oxidized,so it has an atomically thin insulating layer.When molecules adsorb on the surface of the surface-oxidized electrode,the weak interaction between the electrode surface and molecules can promote the spinsplitting in molecular orbitals,so as to make the hybrid interfacial state with a longer lifetime or generate highly spin-polarized current across the hybridized interface.Based on the discussion of molecule adsorption on the properties of the interface for ferromagnetic metals both with and without surface oxidation,we further analyzed the influence of the in-plane and out-of-plane orbitals on the metallic spin-filtering mechanism,the resistive spin-filtering mechanism and the dynamic spin-filtering mechanism.Our results show that both the in-plane and out-of-plane orbital has great influence to metallic spin-filtering,while in-plane orbitals are not important for resistive and dynamic spin-filtering.