Magnetic relaxation pathways in lanthanide single-molecule magnets

Single-molecule magnets are compounds that exhibit magnetic bistability caused by an energy barrier for the reversal of magnetization (relaxation). Lanthanide compounds are proving promising as single-molecule magnets: recent studies show that terbium phthalocyanine complexes possess large energy ba...

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Bibliographic Details
Published in:Nature chemistry 2013-08, Vol.5 (8), p.673-678
Main Authors: Blagg, Robin J., Ungur, Liviu, Tuna, Floriana, Speak, James, Comar, Priyanka, Collison, David, Wernsdorfer, Wolfgang, McInnes, Eric J. L., Chibotaru, Liviu F., Winpenny, Richard E. P.
Format: Article
Language:English
Subjects:
639/638/263/911
639/925/357/997
Analytical Chemistry
Biochemistry
Chemistry
Chemistry/Food Science
Dysprosium
Energy
Inorganic Chemistry
Ions
Lanthanoid Series Elements - chemistry
Ligands
Magnetics
Molecular Structure
Organic Chemistry
Oxidation
Physical Chemistry
Physics
Protons
Terbium
Yttrium
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Summary:Single-molecule magnets are compounds that exhibit magnetic bistability caused by an energy barrier for the reversal of magnetization (relaxation). Lanthanide compounds are proving promising as single-molecule magnets: recent studies show that terbium phthalocyanine complexes possess large energy barriers, and dysprosium and terbium complexes bridged by an N 2 3− radical ligand exhibit magnetic hysteresis up to 13 K. Magnetic relaxation is typically controlled by single-ion factors rather than magnetic exchange (whether one or more 4 f ions are present) and proceeds through thermal relaxation of the lowest excited states. Here we report polylanthanide alkoxide cage complexes, and their doped diamagnetic yttrium analogues, in which competing relaxation pathways are observed and relaxation through the first excited state can be quenched. This leads to energy barriers for relaxation of magnetization that exceed 800 K. We investigated the factors at the lanthanide sites that govern this behaviour. Dysprosium alkoxides and dysprosium-doped yttrium alkoxides show very large energy barriers, greater than 800 K, to magnetic relaxation. These barriers arise from the presence of a strongly axial pseudo-octahedral crystal field, which switches off relaxation through the first excited state that typically occurs in single-molecule magnets, and favours a competitive pathway through higher-energy states.
ISSN:1755-4330
1755-4349
DOI:10.1038/nchem.1707