Anticrossing spectroscopy in multi-nanolayer structures

Abstract

Presently we explored nanosandwich structures with graphite (Gt) and graphene (Gn) nanolayers. We found that in Pt–SiO2–Gt, Pt–BN–Gt and Pt–SiO2–Ni–Gn structures the spectra may be decomposed into several components, each corresponding to a different value of the total spin angular momentum S. Only one component was required to describe the Pt–SiO2–Ni–Gn spectra at 5.3K, with additional components appearing at higher temperatures. On the other hand, a single component described the Pt–BN–Ni–Gn spectra at all temperatures. Temperature dependence of the spectra of the Pt–SiO2–Ni–Gn system was studied in the 5.3–75.3K range. Presently we obtained experimental results for novel sandwich systems, with the Gn layer only two monoatomic layers thick. Thus, we compared experimental spectra of a three-nanolayer sandwich system containing a Gt nanolayer with those of a four-nanolayer system containing a diatomic Gn layer. The experimental results were discussed using a theoretical model of the respective physical mechanisms. We propose an exchange anticrossing mechanism, whereby the spin-state polarization of the given Zeeman׳s substate in the Pt nanolayer is transported to Gt or Ni–Gn nanolayer by the exchange interaction between the two layers. As long as exchange interaction coupling spin states in different nanolayers is involved, we term the respective spectra the “spin anticrossing exchange-resonance spectra”. This clarifies the physical origins of some of the model parameters, i.e. the growing external magnetic field shifts the Zeeman׳s substates in the different layers differently, producing the anticrossing spectrum. In the frameworks of the developed model, we propose spin–orbit (SO) interaction as the main factor inducing the spin–lattice relaxation, which is one of the important factors determining the line shape. We performed ab initio calculations of the SO interaction in carbon and metal nanolayers, finding that the SO interactions monotonously increase with the atomic number.