Magnetic Blocking from Exchange Interactions: Slow Relaxation of the Magnetization and Hysteresis Loop Observed in a Dysprosium–Nitronyl Nitroxide Chain Compound with an Antiferromagnetic Ground State |
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Authors: | Tian Han Dr. Wei Shi Zheng Niu Bo Na Prof. Dr. Peng Cheng |
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Affiliation: | Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE), Nankai University, Tianjin 300071 (P.R. China), Fax: (+86)?22‐23502458 |
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Abstract: | The combination of the anisotropic DyIII ion and organic radicals as spin carriers results in discrete and one‐dimensional lanthanide–radical magnetic materials, namely, [Dy(hfac)3(NITThienPh)2] ( 1 ) and [Dy2(hfac)6(NITThienPh)2]n ( 2 ; hfac=hexafluoroacetylacetonate, NITThienPh=2‐(5‐phenyl‐2‐thienyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide). Linking monomeric 1 with the DyIII ion leads to the formation of polymeric 2 , and the transformation between them is chemically controllable and reversible. The characterization of both static and dynamic magnetic properties shows that the dominant intrachain exchange interaction is important to observe magnetic bistability in 2 rather than that in 1 . Monomeric 1 exhibits paramagnetic behavior, whereas polymeric 2 shows the unusual coexistence of superparamagnetic and two‐step field‐induced metamagnetic behaviors. The antiferromagnetic ground state of 2 does not prevent the dynamic relaxation of the magnetization with the finite‐sized effect in the lanthanide–radical system. Energy barriers to thermally activated relaxation for 2 are 53 and 98 K in the low‐ and high‐temperature regimes, respectively. A hysteresis loop is observed with the coercive field of 99 Oe at 2 K. |
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Keywords: | exchange interactions lanthanides magnetic properties radicals relaxation |
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