Influencia de la reducción del tamaño en las propiedades electrónicas y magnéticas de aleaciones binarias de Tierras Raras

Abstract

This work has been performed within the Magnetism Group at the University of Cantabria. The aim of this is to study the change in the electronic and magnetic properties of binary rare earth alloys when these are taken into the nanometric scale. Thus, we will show in this thesis not only the employed methodology but also the obtained results for two nanometric rare earth compounds: TbCu2 and YbAl3. Alloys were obtained by arc melting and afterwards, its mechanical milling in a planetary ball mill. The measurements that we performed comprise x-ray (in house and at large facilities) and neutron diffraction, DC-magnetisation and AC-susceptibility, specific heat and electrical resistivity. Amongst the most relevant results we can underline several aspects. First, the discovery of the coexistence of a superantiferromagnetic state with a spin glass behavior at low temperatures for the nano-TbCu2. On the other hand, it has been observed in the nano-YbAl3 a minimum in the electrical resistivity (not present in the bulk alloy); this has been explained as a combination of effects: quantum interference effects (specifically the electron-electron interaction) and a change from a Kondo lattice to a Kondo behavior.