Multiple relaxation times in single-molecule magnets

Abstract

Multiple relaxation times detected in the ac magnetic susceptibility of several single-molecule magnets have been always assigned to extrinsic factors, such as nonequivalent magnetic centers or effects of intermolecular interactions in the crystal. By solving quantum relaxation equations, we prove that the observed multiple relaxation times can be of intramolecular origin and can show up even in single-ion metal complexes. For the latter a remarkably good description of the coexistent two relaxation times is demonstrated on several experimental examples. This proves the relevance of the intramolecular mechanism of multiple relaxation times in such systems, which is even easier justified in polynuclear magnetic complexes.

Molecular single-ion magnets based on lanthanides and actinides: Design considerations and new advances in the context of quantum technologies

“…For mononuclear SIMs, the multi-peak feature of ′′ ( ) data has routinely been linked to extrinsic factors, such as the existence of crystallographically inequivalent metal sites, or the occurrence of intermolecular dipolar interactions that occur in the solid state. However, Ho and Chibotaru have recently demonstrated that intrinsic effects can actually give rise to two ac maxima in mononuclear f-SIMs [73].…”

Novel mononuclear and 1D-polymeric derivatives of lanthanides and (η6-benzoic acid)tricarbonylchromium: synthesis, structure and magnetism

“…The presence of two maxima on the χ″(ν) isotherms was previously reported for monometallic complexes. 28,29 The theoretical explanation of the appearance of two maxima was carried out previously 30 . Polymorphism can dramatically change the magnetic behavior of SMM 31 and may also result in the appearance of the second maxima.…”

Rare “Janus”-faced single-molecule magnet exhibiting intramolecular ferromagnetic interactions

“…The [Fe 7 (N 3 ) 12 ] 2+ core is present in both forms of 1 , as confirmed by X-ray diffraction studies (for 1-w ), elemental analyses (for 1-d ) and DC magnetic studies ( S = 14 for both forms). The different number of relaxation processes (two for 1-d and one for 1-w ) and values of energy barriers for the magnetization reversal are attributed to differences in intermolecular interactions49 and the dissimilar molecular anisotropies emanating from different crystal fields around the peripheral Fe II ions.…”