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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
Author(s) -
Han Tian,
Shi Wei,
Niu Zheng,
Na Bo,
Cheng Peng
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201202708
Subject(s) - antiferromagnetism , dysprosium , magnetization , ground state , coercivity , superparamagnetism , relaxation (psychology) , hysteresis , exchange interaction , condensed matter physics , materials science , paramagnetism , lanthanide , chemistry , magnetic hysteresis , crystallography , ion , ferromagnetism , magnetic field , inorganic chemistry , atomic physics , organic chemistry , physics , social psychology , psychology , quantum mechanics
The combination of the anisotropic Dy III 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 [Dy 2 (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 Dy III 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.