Absence of exchange interaction between localized magnetic moments and conduction-electrons in diluted Er3+ gold-nanoparticles

The Electron Spin Resonance (ESR) of diluted Er3+ magnetic ions in Au nanoparticles (NPs) is reported. The NPs were synthesized by reducing chloro triphenyl-phosphine gold(I) and erbium(III) trifluoroacetate. The Er3+ g-value along with the observed hyperfine splitting indicate that the Er3+ impurities are in a local cubic symmetry. Furthermore, the Er3+ ESR spectra show that the exchange interaction between the 4f and the conduction electrons (ce) is absent or negligible in Au1–xErx NPs, in contrast to the ESR results in bulk Au1–xErx. Therefore, the nature of this interaction needs to be reexamined at the nano scale range