First Principles Study On Deposition Of Rare Earth Er Atoms/Clusters On Cu(111) Surface

Magnetic storage technology,the most extensive and important way of information recording,has been developed to read and write information at atomic scale in experiments.It is found that atomic magnetic storage can effectively improve the density of the storage surface,so as to realize the miniaturization of devices and meet the development needs of the information society.When exploring the date storage system at the limit scale,the surface deposited single magnetic atom/cluster structure has become a research hotspot in recent years due to its remarkable magnetic merits.There is an unfilled 4f electron layer in the outer layer of rare earth atoms,which leads to rare earth atoms with sizable spin and orbital magnetic moments.At the same time,the 4f electrons are embedded in the inner layer of 5s25p66s2 can shield the interaction with neighboring particles,which can shield the interaction with neighboring electrons and form a large local magnetism.In particular,the strong spin orbit coupling(SOC)of rare earth atoms can be coupled with the lattice,which can effectively improve the magnetic anisotropy(MAE)and magnetic stability of the magnet,and enhance the ability of the system to resist thermal disturbance.Therefore,the research on the surface deposition of rare earth atoms/cluster is not only helpful to understand the micro mechanism of magnetic properties of rare earth materials,but also has potential application value in spintronics and quantum computing.This paper is based on density functional theory(DFT)and considers a variety of methods to deal with electron strongly correlated systems,we systematically studied the composite system of Er clusters deposited on Cu(111)surface,namely Ern@Cu(111)(n=1,2,3).We analyzed the deposition configuration and ground state electronic structure,get the magnetic information such as spin magnetic moment,orbital magnetic moment,MAE,etc.The main contents and conclusions are summarized as follows:(1)Through the analysis of interaction energy,adsorption energy and free energy,the most stable deposition structure of Er on Cu(111)surface is the bridge site adsorption.Similarly,dimer and trimer clusters also tend to adsorb on the bridge sites,forming stable structures with double and three bridge sites.With the increase of the number of Er atoms,the adsorption energy decreases and the binding energy increases,which indicates that the stability of the system increases.(2)Based on the U value(U=7.867 eV)fitted by linear response method,DFT+U calculation was carried out for the system.It is found that the direction of the easy axis of a single atom is in the plane,and its magnetic moment is ?1=4.98?B/atom(?S1=1.80?B,?L1=3.18 ?B).The easy axis of Er2 and Er3 is in the opposite direction of out of plane,and the corresponding magnetic moment is ?2=5.18 ?B/atom(?S2=1.81 ?B,?L2=3.37 ?B)?3=4.74?B/atom(?S3=1.54?B,?L3=321?B).And the MAE value of the system increases with the increase of atomic number(24.78?46.81 meV/atom).(3)Using the occupation number method,i.e.considering 21 occupation modes of Er 4f orbital,the single atom deposition system is found Er@Cu(111).It is fund that the lowest occupied state of single deposition system is[1110110],and the energy difference between the magnetic ground state and other occupied states is large(0.001-2.174 eV),which indicates that the ground state electron arrangement can be obtained by using the occupation number method,thus can effectively avoiding the metastable state of the system and reaching the real ground state.(4)Combined with the electronic structure and the second-order perturbation method,the spin orbit coupling tensor of the system is calculated,and the MAE source of the deposition system is analyzed.It is found that the MAE mainly due to the transition between orbits(m=±3)of 4f electrons under the effect of spin orbit coupling.In this paper,through the analysis of Ern@Cu(111)(n=1,2,3)systematic analysis has obtained the deposition composite structure with high stability and high MAE,which has deepened people's understanding of the magnetic microscopic mechanism of rare earth clusters and provided a feasible scheme for dealing with the electron strong correlation system.At the same time,it provides a reliable theoretical basis for the experimental phenomenon,and also provides a theoretical support for the exploration of rare earth materials as data storage materials.