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Progress in the magnetic exchange study achieved by a team led by Prof. Yan-Zhen Zheng in FIST, Xi’an Jiaotong University
Hits:    Update:2017/12/6 14:22:03

 

Understanding magnetic interactions is at the heart of molecular magnetism, which leads to the exciting discovery of single-molecule magnets, single-chain magnets, molecular magnetic refrigerants, spin-based qubits and single-molecule toroics. Cyclic polymetallic compounds are of particular interest as models of infinite 1D chains, but with finite size, which may provide deeper insight to the magnetic interactions and excitations including the homo- and hetero- spin systems. However, the magnetic states increase exponentially with the increase of number of metal ions, which makes it hard to investigate the magnetic exchanges accurately.
Recently, under the guidance of Professor Yan-Zhen Zheng in Xi'an Jiaotong University, the postgraduate student Lei Qin successfully synthesized a large Cr(III)-Ln(III) hetero-spin wheel {Cr8Ln8} with sixteen alternating Cr(III) and Ln(III) metal centers. Ascribed to the high symmetry of {Cr8Gd8}, the quantum Monte Carlo (QMC) calculations reveal the antiferromagnetic interactions in the system with average magnetic exchange parameter of 2.1 K, suggesting a well isolated ferrimagnetic spin ground state (ST = 16). Further high-field magnetization measurement agrees well with the QMC simulation studies and confirms the exchange-coupling constant within the ring. Moreover, the Dy analogue {Cr8Dy8} shows slow magnetic relaxation and non-tunneling zero-field magnetic hysteresis loop at low temperatures which suggests the presence of magnet behavior. Together with the absence of frequency-dependent ac susceptibility of a diluted sample {Cr8Dy0.046Y0.954}, the slow magnetic relaxation behavior is confirmed to originate from the whole molecule rather than from the single dysprosium ions, which is very rare in giant 3d-4f cyclic cages. The distinct magnetic behavior of the Gd and Dy analogues in this sixteen-membered hetero-spin 3d-4f ring can be vividly shown in the following picture.
 
This work was collaborated with Prof. L. Engelhardt (Francis Marion University, USA), Prof. H. Nojiri (Tohoku University) and Prof. R. E. P. Winpenny (University of Manchester) and supported by the key international joint project of NSFC (Grant No. 21620102002), Wuhan National High Magnetic Field Center (2015KF06), the Cyrus Chung Ying Tang Foundation and Fundamental Research Funds for the Central University. The result was published in the journal Angewandte Chemie International Edition (IF = 11.99), entitled as “Quantum Monte Carlo Simulations and High-Field Magnetization Studies of Antiferromagnetic Interactions in a Giant Hetero-Spin Ring” (DOI: 10.1002/anie.201709650). Link to the paper can be found: http://onlinelibrary.wiley.com/doi/10.1002/anie.201709650/full.
 
Prof. Yan-Zhen Zheng is a Young Top-Notch Talent (A level) professor in Frontier Institute of Science and Technology (FIST), Xi’an Jiaotong University. His research interests include molecular magnetism and functional coordination clusters.
Group website: http://gr.xjtu.edu.cn/web/zheng.yanzhen/home
CACR (FIST) website: /center/CACR/
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