Exchange interaction between localized magnetic moments and conduction-electrons in Er doped gold nanoparticles synthesized by laser ablation in water

Abstract

In this work, we report a fundamental study on the exchange interaction between localized rare earth magnetic moments and conduction electrons of Er3+ diluted in Au metallic nanoparticles (NPs) produced by laser ablation in liquid. The study was carried out in Au1−xErx (x ≤ 0.026) bulk metallic alloys and NPs with a mean size of 20 nm. The samples were characterized by means of x-ray diffraction, transmission electron microscopy, magnetic susceptibility, and electron spin resonance (ESR) experiments. The obtained results showed that, despite the high temperature and being far away from chemical equilibrium throughout the laser ablation process, in the AuNPs, the Er3+ (J = 15/2) ground state of the crystal electric field split multiplet remains a Γ7 (g = 6.79) Kramers doublet with the expected g-shift and T-dependence of the ESR linewidth, preserving the general bulk properties and the cubic symmetry. In addition, the Au1−xErx NPs present narrow ESR residual linewidth suggesting homogeneous Er3+ doping and negligible strain distribution in the Au1−xErx NPs. This new methodology may certainly provide relevant insight into the study of the intrinsic physical properties of dilute rare earth metallic alloys at the nanometer scale seeking quantum size effects and motivates novel technological applications.