title: Zero-Point Spin-Fluctuations of Single Adatoms.
abstract: Stabilizing the magnetic signal of single adatoms is a crucial step toward 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 ≳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.
authors.affiliation: Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, D-52425 Jülich, Germany.
authors.forename: Julen
authors.initials: J
authors.lastname: Ibañez-Azpiroz
authors.affiliation: Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, D-52425 Jülich, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Dos Santos Dias
authors.affiliation: Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, D-52425 Jülich, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Blügel
authors.affiliation: Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, D-52425 Jülich, Germany.
authors.forename: Samir
authors.initials: S
authors.lastname: Lounis
keywords: Spin dynamics; density functional theory; magnetic anisotropy energy; single adatoms