Ultimate Manipulation of Magnetic Moments in the Golden Tetrahedron Au₂₀ with a Substitutional 3d Impurity

Abstract

Nanocluster systems that are electronically stable and highly magnetic have been of intense research interest due to their potential as magnetic superatoms. In this study, we consider a more intriguing case of the unique golden pyramid with a substitutional 3d impurity. In particular, we investigate the geometry, stability, and magnetic properties of Au19M clusters (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) by means of density functional theory calculations. It is found that the structural patterns of doped species evolve from endohedrally doped cages to exohedrally doped tetrahedrons when M goes from Sc to Cu. The robustness of the Au20 unit tends to be retained in its tetrahedral doped counterparts. Remarkably, the quenched magnetic moment of Au20 increases in a systematic manner with the appearance of 3d impurities. We demonstrate that not only the interaction between the magnetic impurity and valence electrons of the Au host but also the itinerant behavior of the impurity valence states have been taken into account to understand the magnetism of Au19M clusters.

Systematic Investigation of the Structure, Stability, and Spin Magnetic Moment of CrMn Clusters (M = Cu, Ag, Au, and n = 2–20) by DFT Calculations

“…It is worth mentioning that the BP86 functional has been proved to yield the most reliable results for different transition-metal-doped coinage metal systems. 16,17,[20][21][22]28 ■ RESULTS AND DISCUSSION Equilibrium Geometries and Growth Mechanism. An extensive search for global minima of CrCu n , CrAg n , and CrAu n with n equal to 2−20 is carried out and their corresponding ground-state structures are shown in Figure 1.…”

“…in which E(Cr), E(M), E(CrM n ), and E(M n+1 ) are the total energies of Cr, M, CrM n , and M n+1 , respectively. In Figure 2a 16,17 The relative stability of CrM n among neighboring sizes is analyzed using the second-order different energy (Δ 2 E) as follows…”

“…One of the emerging questions is to rationalize the interaction between localized impurity states and free electron gas, which allows us to detect the smallest limit from where complex phenomena as Friedel oscillations and the Kondo effect show up. − In this regard, the behavior of a coinage metal cluster doped with a transition-metal atom, where the electron cloud is well-controlled by the number of metal atoms in a cluster while the number of localized valence electrons is specified by the transition-metal atom, has been of significant interest. − For instance, the Fe and Co atoms in Ag n Co + and Ag n Fe + were found to usually delocalize 4s electrons, but their all 4s and 3d valence electrons can be fully itinerant at specific sizes, i.e., Ag 10 Co + and Ag 11 Fe + . A similar electronic configuration was predicted for neutral Ag 10 Fe, where the cluster magnetic moment is completely quenched due to the closed 18-electron shell structure .…”

Iron doped gold cluster nanomagnets: ab initio determination of barriers for demagnetization

“…[2][3][4][5][6][7] Gold clusters usually exhibit small (S ¼ 0, 1/2) spin quantum numbers, leading to closed shell or doublet electronic ground states but doping them with a transition metal atom can lead to open-shell clusters with signicantly higher spin-quantum numbers. [8][9][10][11][12][13][14] For example, Tam et al 12 investigated the structure and stability of transition metal doped golden pyramids Au 19 M (M ¼ Cr, Mn, Fe) at the level of generalized gradient density functional theory (DFT). All systems show higher ground state spin quantum numbers, while the structural modications are minor.…”

“…Several studies have investigated transition metal doped gold clusters using DFT. [8][9][10][11][12][13][14] These studies focused on predicting stable structures and their spin quantum numbers. On the other hand, several studies examined magnetic properties of transition metal complexes, i.e., a transition metal ion surrounded by a primarily organic framework, with wave function based, multireference perturbation theory methods.…”