Theory Study On Enhanced Magnetism And Magnetic Anisoyropy Of Mn-based And Cu-based Alloy Clusters

Transition metal clusters exhibit unique magnetic properties due to their unfilled d-electronic structure,which can be governed by the alloying of clusters to obtain tailorable new materials.And this clusters induce a number of potential applications in high-density magnetic recording and biomedical fields and so on.A large number of experiments and theoretical results show that the magnetic moment of clusters can be strengthened by appropriate atom doping.The enhanced magnetism has been found in ferromagnetic clusters doped with Mn.However,the effect is unsatisfactory for transition metal clusters with antiferromagnetic arrangement,and they gradually lose their application value.How to change this situation so that the clusters can release huge magnetism and reuse this material has become a concern for us.In this paper,theoretical studies on Mn and Cu clusters with the above problems are carried out.On this basis,diverse atoms with different quantities are doped to increase the magnetic properties of Mn-based and Cu-based clusters.The main research are as follows:（1）First principles study of bimetallic Mn_13-nCo_n（n=0-13）clusters:structural,magnetic evolution and effects of spin-orbit couplingThe ground state structures,spin,orbital magnetic moment and magnetic anisotropy of bimetallic clusters Mn_13-nCo_n（n=0-13）are systematically investigated by using DFT-GGA with and without spin-orbit coupling.The studies reveal a transition from icosahedron（ICO）to the hexagonal bilayer（HBL）structure,following the rule putting Mn in a central position and Co in the surface of icosahedrons.The magnetic moments of clusters increase to the maximum in Mn₉Co₄（39μ_B）and then decrease as a function of Co concentration.Besides,we find that the orbital moments of all clusters are dominated by Co atoms,as the composition of Co increases,the orbital moments are increased from 0.01μ_B(Mn₁₃)to 1.34μ_B(Co₁₃).However,magnetic anisotropy and magnetic anisotropy energy（MAE<10 meV）are not evident in all clusters.（2）Magnetism of TM@Cu₁₂@N₁₂（TM=Mn,Fe,Co,Ni,Cu,Ru,Rh,Pd,Ir,Pt）nanoclusters from first-principles studyThe stability of structures,spin,orbital magnetic moment and magnetic anisotropy energy of TM@Cu₁₂@N₁₂（TM=Mn,Fe,Co,Ni,Cu,Ru,Rh,Pd,Ir,Pt）are investigated systematically by using PBE+U with and without spin-orbit coupling.The results show that the nitrogen atoms absorbed on the surface of Cu₁₃ cluster deform the Cu₁₃ structure singnificantly,and the stabilities of the clusters are enhanced by the formation of Cu-N and Cu-TM bonds.The N-capped clusters more perfer to produce larger magnetic moment.In addition,the magnetic environment of clusters is improved by doping TM（TM=Mn、Fe、Co、Ni、Cu、Ru、Rh、Pd、Ir、Pt）atoms,which result in TM@Cu₁₂@N₁₂2 clusters present various magnetic properties.For instance,the doping of 3d atoms further increase the spin magnetic moment of the clusters and the magnetic anisotropy energy of the cluster is remarkably improved by doping Rh and Pt atoms,though the orbital moments of clusters are not relesed by 4d and 5d atoms.