Theoretical Study On The Magnetic Properties Of Single-molecule Magnets

Single-molecule magnets (SMMs) have attracted great interest because of their versatile intriguing architectures and potential applications such as quantum computing, high-density memory storage devices, and magnetic refrigeration. In this paper, we select two kinds of new synthesized SMMs representing the trend during the past few years and explored their magnetostructural correlations using Ab initio calculations method.For[(Cp*2Ln)2(?-pym)]+(Ln=Gd?(1),Tb?(2),Dy?(3),Cp*=pentamethylcyclopenta-dienyl),bpym-(bpym= 2,2'-bipyrimidine),CASSCF calculations on four Ln fragments indicate that the single Ln anisotropy energy barriers of 2 and 3 are far larger than those of 4 and 5, but their total energy barriers are much smaller. Since 4 and 5 have stronger Ln-bpym- coupling interactions than2 and 3.Thus, to enhance the total energy barrier, it needs to enhance the Ln-bpym- couplings interaction when improves the single Ln fragment barrier at the same time.Among[Dy2Ni2(C12H14NO5)2(?3MeO)2(CH3CN)2(NO3)4]·4H2O(1),[Ln2Ni2(C11H12 N-O4)2(?3MeO)2(CH3CN)2(NO3)4]·4H2O(Ln=Tb(2),Dy(3)),[Dy4Co2(C11H11NO4)2(?3-OH)2((CH3)3CCOO)10(OH2)2]·2(CH3)3CCOOH·2CH30H·5H20(4),the total barrier of 4 is only 20.4 cm-1 although the energy separation between the ground and the first excited state of one Dy ion is up to 305.2 cm-1. however.1,2 and 3 which total energy barriers are much larger than 4, especially for 2, the energy barrier is up to 60.3 cm-1. Since they have stronger 3d-4f coupling interactions than 4. And all of those Dy-Dy interactions are relatively much weaker. The above results show that the two Ln ions may have much more contribution to the total barrier through the stronger 3d-4f exchange couplings interaction compared to those with weak Ln-Ln interactions.