Size- and Temperature-Dependent Magnetic Response of Molecular Cage Clusters: Manganese-Doped Tin Clusters

Abstract

Endohedral clusters, formed by incorporating a single Mn atom into a cage of tin atoms, have been generated in the gas phase. Mass spectrometry reveals that a cage size of 10 tin atoms is necessary for the efficient incorporation of one Mn atom. Some of the cluster compounds with one Mn atom attached to the tin clusters display large intensities compared to the pure tin clusters, indicating that the compound clusters are particularly stable. The manganese-doped tin cluster assemblies Mn@Sn12, Mn@Sn13, and Mn@Sn15 have been further analyzed within a molecular beam magnetic deflection experiment. Interestingly, although the effect of the magnetic field on the behavior of Mn@Sn12 is quite different from that of Mn@Sn13 and Mn@Sn15, the magnetic dipole moments are the same within the uncertainty of the measurements. Magnetic dipole moments have been found in close agreement with the spin quantum number S = 5/2 predicted by theory for Mn@Sn12, indicating that the magnetic moment of the Mn atom is not quenched. This supports the idea that within a tin cluster cage a single Mn atom can be encapsulated, resulting in the formation of endohedral clusters consisting of a central Mn2+ ion surrounded by a particularly stable Zintl-ion cage Sn(N)(2-). The observed molecular beam profiles indicate that at a nozzle temperature of 55 K the magnetic moment is strongly locked to the molecular framework of Mn@Sn12; in contrast, the magnetic moment of Mn@Sn13 and Mn@Sn15 tends to align with the magnetic field. The experiments therefore demonstrate that the size of a presumably nonmagnetic cluster cage might have a fundamental influence on the magnetization dynamics of paramagnetic species. The influence of vibrational excitation on the Stern-Gerlach profile of Mn@Sn12 is further analyzed, and it is shown that the behavior of Mn@Sn12 at elevated nozzle temperatures changes continuously toward a nonlocked moment, pointing to size- and temperature-dependent magnetization dynamics.

Atomic domain magnetic nanoalloys: interplay between molecular structure and temperature dependent magnetic and dielectric properties in manganese doped tin clusters

“…The magnetic response of tin clusters doped with a single Mn atom depends critically on the size and temperature of the clusters. 22,23 In order to rationalize these observations, we study the Mn/Sn N clusters by quantum chemistry (QC) methods combined with an evolutionary inspired optimization of the tin cage. Stark experiments are analyzed in order to identify the molecular structure of the clusters from simulations of the dielectric response.…”

“…In recent publications 22,23 we investigated the dependence of spin angular momentum orientation on the size and temperature of Mn@Sn N clusters (N = 12, 13, 15). The specific molecular structure of Mn@Sn 12 (I h ) gives rise to quasi atomic magnetic response in the vibrational ground state, whereas excited normal modes that break the spin microstate degeneracy induce spin orientation.…”

Photoelectron spectra and structure of the Mnn− anions (n = 2–16)

“…kbowen@jhu.edu atom to a magnetic or nonmagnetic cluster results [11][12][13][14][15][16] in an increase of the total cluster spin magnetic moment by 3-5 µ B , whereas adding a single 3d-metal atom 17 to Mn 12 or a nitrogen atom 18 to Mn n can increase their total spin magnetic moments by an order of magnitude. Manganese is widely used for doping semiconductor quantum dots (QD).…”

Mass spectrometry and its role in advancing cluster science

“…Here cationic clusters Bi x Na y + l + , corresponding to Bi x yÀ , appear as magic numbers in the distribution for every reported anionic Zintl ion of bismuth. From the observation of Bi 3 Na 4 + as a magic number in the mass spectrum in within the cluster anions (Na 3 Sn 4 ) À , (NaGa 4 ) À , (KSn 12 ) À , and (KPb 12 ) À , respectively, as well as endohedral [M@Pb 12 ] 2À and [M@Sn 12 ] 2À where M is a transition metal atom have been studied through a combination of anion photoelectron spectroscopy and theorertical calculations [84][85][86][87][88][89][90]. Recently, aluminum moieties within selected Na-Al clusters have been shown to exhibit Zintl characteristics [90].…”