| Single-molecule magnets have potential applications in the fields of high density information storage,spintronics,magnetic refrigeration and quantum computing.Due to the large unquenched orbital angular momentum in the ground state of lanthanide ions and the large spin-orbit coupling,the single-molecule magnet composed of lanthanide ions has a large magnetic anisotropic barrier.In this paper,a series of binuclear dysprosium monomolecular magnets were selected,and the source of magnetic anisotropic energy barrier and its magnetic relaxation mechanism were calculated.In this paper,three types of binuclear dysprosium monomolecular magnets were selected and their structure activity relationships and relaxation mechanisms were investigated by ab initio calculation.First,two structrally similar compounds Dy2L2?NO3?2?EtOH?2?1?and Dy2L2?NO3?2?MeOH?2?2?were calculated.They are composed of 2-ethoxy-6-{??2-hydroxy-3-methoxybenzyl?imino?methyl}phenol?H2L?as a chelate ligand and the binding alcohols?EtOH and MeOH?as the auxiliary ligands.The results of ac susceptibility test show that the two compounds exhibit the behavior of monomolecular magnets in the zero dc field.The magnetic anisotropy of single Dy? in compound 1 and 2 is similar,but the effective energy barrier after fitting is 131.3 K?1?and 198.8 K?2?,respectively.In this chapter,by studying the effects of different end group ligands on the coupling between Dy? and resulting in the difference between the effective energy barrier of compounds 1 and 2,an effective way is provided for the synthesis of high energy barrier binuclear dysprosium molecular magnets.Secondly,two hetermetallic Zn2Dy2 cluster compounds[Zn2Dy2?L?4?CH3COO?2?CH3CH2OH?]2CH2Cl2·0.5H2O?1?and[Zn2Dy2?L?4?CH3CO-O?2?CH3OH?2]4CH2C l2·2CH3OH·0.1H2O?2?were calculated with similar structure and central symmetry.Theoretical calculations show that the difference in magnetic properties between 1 and 2 is mainly due to the change in coordination mode of acetic acid anions at the Dy? site.By subtle modification of the alcohol solvent resulted in different magnetic behaviors of two similar binuclear heterometal compounds,which provided a new direction for obtaining the binuclear dysprosium monomolecular with high energy barrier.Finally,the magnetic properties of the compound[Dy2Zn2?La?2?bpdc?2Cl2]·3MeOH?1?and[Dy2Zn2?Lb?2?bpdc?2Cl2]·MeOH·H2O?2?were investigated theoretically.There are two types of Dy? ions in compounds 1 and 2,and the effective energy barrier of compounds can be changed by adjusting the length of the diimine chain of schiff base ligands in two asymmetric hetermetallic Zn2Dy2cluster compounds.The theoretical calculation and analysis of the magnetic anisotropy of the above compounds indicate that the energy barrier of the dysprosium binuclear compounds mainly comes from the dysprosium mononuclear,and the coupling between dysprosium and dysprosium has a great influence on the energy barrier.Therefore,in order to improve the barrier of the dinuclear dysprosium single-molecule magnet,the barrier of the monuclear dysprosium must be increased.Moreover,the magnetic axes on the dysprosium should be oriented as far as possible along their lines to reduce the effect of the coupling poles of the dysprosium on the probability of mononuclear tunneling. |
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