Origins of Slow Magnetic Relaxation in Single-Molecule Magnets

Exponential and power law temperature dependences are widely used to fit experimental data of magnetic relaxation time in single molecular magnets. We derived a theory to show how these rules arise from the underling relaxation mechanisms and to clarify the conditions for their occurrence. The theor...

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Bibliographic Details
Published in:Physical review letters 2020-09, Vol.125 (11), p.1-117203, Article 117203
Main Authors: Gu, Lei, Wu, Ruqian
Format: Article
Language:English
Subjects:
Coupling (molecular)
Magnetic anisotropy
Magnetic induction
Magnetic relaxation
Magnets
Phonons
Physics
Relaxation time
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Summary:Exponential and power law temperature dependences are widely used to fit experimental data of magnetic relaxation time in single molecular magnets. We derived a theory to show how these rules arise from the underling relaxation mechanisms and to clarify the conditions for their occurrence. The theory solves the puzzle of lower-than-expected Orbach barriers found in recent experiments, and elucidates it as a result of the Raman process in disguise. Our results highlight the importance of reducing the rate of direct tunneling between the ground state doublet so as to achieve longtime coherence in magnetic molecules. To this end, large spin and small transverse magnetic anisotropy can reduce magnitude of the transition operator, and rigid ligands may weaken the spin-phonon coupling in that they raise the energy of vibrational modes and better screen the acoustic phonons.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.125.117203