We report a combined experimental and theoretical study to ascertain carbon solubility in nickel nanoparticles embedded into a carbon matrix via the one-pot method. This original approach is based on the experimental characterization of the magnetic properties of Ni at room temperature and Monte Carlo simulations used to calculate the magnetization as a function of C content in Ni nanoparticles. Other commonly used experimental methods fail to accurately determine the chemical analysis of these types of nanoparticles. Thus, we could assess the C content within Ni nanoparticles and it decreases from 8 to around 4 at. % with increasing temperature during the synthesis. This behavior could be related to the catalytic transformation of dissolved C in the Ni particles into graphite layers surrounding the particles at high temperature. The proposed approach is original and easy to implement experimentally since only magnetization measurements at room temperature are needed. Moreover, it can be extended to other types of magnetic nanoparticles dissolving carbon.
The slave boson (SB) technique is employed to study the Zeeman spin splitting in a quantum dot. Unlike traditional SB method, each spin is renormalized differently. Two geometries are compared: side connected and embedded. In both cases, it's shown a non linear behavior of the splitting as a function of the magnetic field applied. The results are in line with the latest experiments.
The splitting of the Kondo Resonance (KR) in a quantum dot (QD) connected to ferromagnetic leads is studied using a new Slave Boson formulation. We show that the KR is splitted into two resonances out of the Fermi level. The splitting can be controlled by the application of a magnetic field in the QD. While this magnetic field does not modify the magnetism of the leads, it can restore the KR at the Fermi level. When the magnetization is strong enough, it's not possible to recover the KR. In addition, selective spin transport across the QD can be achieved by tuning the magnetic field. This effect is a consequence of the asymmetric Kondo splitting produced by the magnetic leads.
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