Abstract
A comprehensive understanding of the ligand field and its influence on the degeneracy and population of d-orbitals in a specific coordination environment are crucial for the rational design and enhancement of magnetic anisotropy of single-ion magnets (SIMs). Herein, we report the synthesis and comprehensive magnetic characterization of a highly anisotropic CoII SIM, [L2Co](TBA)2 (L is an N,N′-chelating oxanilido ligand), that is stable under ambient conditions. Dynamic magnetization measurements show that this SIM exhibits a large energy barrier to spin reversal Ueff > 300 K and magnetic blocking up to 3.5 K, and the property is retained in a frozen solution. Low-temperature single-crystal synchrotron X-ray diffraction used to determine the experimental electron density gave access to Co d-orbital populations and a derived Ueff, 261 cm-1, when the coupling between the dx2 - y2 and dxy orbitals is taken into account, in very good agreement with ab initio calculations and superconducting quantum interference device results. Powder and single-crystal polarized neutron diffraction (PNPD, PND) have been used to quantify the magnetic anisotropy via the atomic susceptibility tensor, revealing that the easy axis of magnetization is pointing along the N-Co-N′ bisectors of the N,N′-chelating ligands (3.4° offset), close to the molecular axis, in good agreement with complete active space self-consistent field/N-electron valence perturbation theory to second order ab initio calculations. This study provides benchmarking for two methods, PNPD and single-crystal PND, on the same 3d SIM, and key benchmarking for current theoretical methods to determine local magnetic anisotropy parameters.
Original language | English |
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Pages (from-to) | 429-440 |
Number of pages | 12 |
Journal | JACS Au |
Volume | 3 |
Issue number | 2 |
DOIs | |
State | Published - Feb 27 2023 |
Funding
S.K.G. is associated with the Research Training Group BENCh (RTG 2455) funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, 389479699). S.K.G. thanks the Alexander von Humboldt Foundation and the International Centre of the University of Göttingen for postdoctoral research fellowships. The purchase of the SQUID magnetometer was supported by the DFG (project number INST 186/1329-1 FUGG) and the Niedersächsische Ministerium für Wissenschaft und Kultur (MWK). J.O. acknowledges funding from Danscatt, the Danish Ministry for Higher Education and Science (SMART and Q-MAT Lighthouses), Villum Foundation, and the Novo Nordisk Foundation. E.F. and H.B.C. are supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Early Career Research Program Award KC0402020, under Contract No. DE-AC05-00OR22725. This research used resources at the High Flux Isotope Reactor and the Spallation Neutron Source, the DOE Office of Science User Facility operated by ORNL. We thank Zachery Morgan for assistance with single crystal PND data reduction. The numerical results presented in this work were obtained at the Centre for Scientific Computing, Aarhus (http://phys.au. dk/forskning/cscaa). Support by the Open Access Publication Funds of the University of Göttingen is gratefully acknowledged.
Keywords
- cobalt single-ion magnet
- experimental electron density
- magnetic anisotropy
- magnetic blocking
- polarized neutron powder diffraction
- single-crystal polarized neutron diffraction
- single-crystal synchrotron X-ray diffraction