Magnetic properties of O2adsorbed on Cu(100): A spin-polarized metastable He beam study

Abstract

Magnetic properties of O 2 adsorbed on Cu(100) were investigated by monitoring the spin dependence in Penning ionization of metastable He(2 3 S) under external magnetic fields of 0-5 T. A clear spin polarization was found for the 3σ g and 1π u orbitals of physisorbed O 2 under external fields, while the spin polarization disappeared when O 2 was changed into the chemisorbed state at >50 K. The magnetic susceptibility at the surface of multilayer and monolayer of physisorbed O 2 on Cu(100) was similar to that for the bulk liquid O 2 . Observed exchange splittings and spin polarization suggest that a physisorbed O 2 molecule has a magnetic moment close to that for an isolated O 2 molecule even at submonolayer coverages, while a density functional theory calculation predicts a much reduced magnetic moment for O 2 directly adsorbed on Cu(100).

Spin Correlation inO2Chemisorption on Ni(111)

“…As has been pointed out by recent theoretical studies [3][4][5], the behavior of the charge and spin of O 2 during its approach to a surface is the key to understanding the dynamics of O 2 dissociation. Conventional density functional theory (DFT) calculations based on the Born-Oppenheimer approximation have predicted that substantial charge redistribution occurs between O 2 and the surface, reducing the O 2 magnetic moment continuously as O 2 approaches the surface [3,6,7]. The validity of such calculations has been doubted because the predicted dissociation barriers are sometimes much lower than those expected from sticking experiments.…”

Tuning Nanoscale Friction by Applying Weak Magnetic Fields to Reorient Adsorbed Oxygen Molecules

“…Molecules initially adsorb in a direction preferentially parallel to the substrate, then progressively tilt upward as coverage increases. The behavior, which is very general for physisorbed oxygen monolayers, has been reported for graphite [22,[25][26][27][28][29][30][31][32] and Ni(111) substrates coated with disassociated oxygen atoms [33][34][35][36]. Above monolayer coverage, a surface melted second layer forms atop the monolayer that is incommensurate with the layer adjacent to the substrate [29,30].…”

“…Measurements were recorded by means of a quartz crystal microbalance (QCM) at 47 K, where oxygen molecules are physisorbed to the substrate and known to remain in a magnetic state upon uptake on the surface [25][26][27][28][29][30][31][32][33][34][35][36]. At 47 K, adsorbed oxygen layers are liquid, but close to their two-dimensional solid-liquid monolayer melting point, and have structural orientation imposed by the substrate.…”