Cu(II)-Dy(III) and Co(III)-Dy(III) based single molecule magnets with multiple slow magnetic relaxation processes in the Cu(II)-Dy(III) complex

摘要

Two dinuclear Schiff-base complexes [(CuDyIII)-Dy-II] and [(CoDyIII)-Dy-III] have been synthesized and structurally characterized. The AC susceptibility measurements taken at B-DC = 0.2 T show a slow magnetic relaxation typical for single-molecule magnets. Unusual is the presence of three relaxation branches in [(CuDyIII)-Dy-II]; the slowest (low-frequency) process possesses the barrier to spin reversal of U/k(B) = 2.8 K and an extrapolated relaxation time as slow as tau(0) = 0.11 s. The intermediate-frequency process is typical for SMM of this class with U/k(B) = 122 K and tau(0) = 9.9 x 10(-7) s; an onset of the high-frequency process is evidenced and this is the fastest. In contrast, the [(CoDyIII)-Dy-III] complex free of exchange coupling exhibits only a single relaxation path with SMM parameters U/k(B) = 113 K and tau(0) = 7.0 x 10(-9) s.