Zero-point spin-fluctuations of single adatoms

Abstract

Stabilizing the magnetic signal of single adatoms is a crucial step towards their successful usage in widespread technological applications such as high-density magnetic data storage devices. The quantum mechanical nature of these tiny objects, however, introduces intrinsic zero-point spin-fluctuations that tend to destabilize the local magnetic moment of interest by dwindling the magnetic anisotropy potential barrier even at absolute zero temperature. Here, we elucidate the origins and quantify the effect of the fundamental ingredients determining the magnitude of the fluctuations, namely the ($i$) local magnetic moment, ($ii$) spin-orbit coupling and ($iii$) electron-hole Stoner excitations. Based on a systematic first-principles study of 3d and 4d adatoms, we demonstrate that the transverse contribution of the fluctuations is comparable in size to the magnetic moment itself, leading to a remarkable $\gtrsim$50$\%$ reduction of the magnetic anisotropy energy. Our analysis gives rise to a comprehensible diagram relating the fluctuation magnitude to characteristic features of adatoms, providing practical guidelines for designing magnetically stable nanomagnets with minimal quantum fluctuations.

arXiv comment16 pages, 5 figures

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• DFT+U Investigation of magnetocrystalline anisotropy of Mn-doped transition-metal dichalcogenides monolayers
• Longitudinal and transverse spin relaxation times of magnetic single adatoms: an ab initio analysis
• Tuning paramagnetic spin-excitations of single adatoms
• Zero-point quantum swing of magnetic couples
• Ab initio investigation of impurity-induced in-gap states in Bi${}_2$Te${}_3$ and Bi${}_2$Se${}_3$
• Spin dynamics of $3d$ and $4d$ impurities embedded in prototypical topological insulators
• Spin-fluctuation and spin-relaxation effects of single adatoms from first principles
• Microscopic theory of spin-relaxation of a single Fe adatom coupled to substrate vibrations
• Engineering elliptical spin-excitations by complex anisotropy fields in Fe adatoms and dimers on Cu(111)
• Investigation of magnetic properties of $4f$-adatoms on graphene
• 3d-oxide molecules to tailor large magnetic anisotropy energies on MgO films