Magnetic Relaxation Dynamics of a Centrosymmetric Dy2 Single-Molecule Magnet Triggered by Magnetic-Site Dilution and External Magnetic Field.

Abstract

A centrosymmetric Dy2 single-molecule magnet (SMM) and its doped diamagnetic yttrium analogues, Dy0.19Y1.81 and Dy0.10Y1.90, were solvothermally synthesized to investigate the effects of intramolecular exchange coupling and quantum tunneling of magnetization (QTM) on the magnetic relaxation dynamics. Constructed from two hula-hoop-like DyIII ions and a pair of phenoxido groups, the antiferromagnetically coupled Dy2 exhibits a thermal-activated zero-field effective energy barrier (Ueff) of 277.7 K and negligible hysteresis loop at 2.0 K. The doping of a diamagnetic YIII matrix with 90.5% and 95.0% molar ratios reveals the single-ion origin of the Orbach channel, increases the relaxation time by partially quenching the QTM process, and induces an open hysteresis loop until 5.0 K. In contrast, an optimal dc field of 1.0 kOe improves the barrier height up to 290.1 K through complete elimination of the QTM and delays the relaxation time of the direct relaxation pathway. More interestingly, the collaborative dual effects of magnetic-site dilution and external magnetic field make the effective energy barrier and relaxation time increase 8.1% and 49 times, respectively. Thus, the overall magnetization dynamics of the Dy2 system systematically elaborate the inherent interplay of the QTM and Orbach processes on the effective energy barrier, highlighting the vital role of the relaxation time on the coercive hysteresis loop.