Point-contact spectroscopy on URu2_2Si2_2

Tunnel and point contact experiments have been made in a URu$_2$Si$_2$ single crystal along the c-axis. The experiments were performed changing temperature and contact size in a low temperature scanning tunneling microscope. A resonance develops at the Fermi level at $T\sim 60$ K. This resonance splits and becomes asymmetric when the 17.5 K phase transition is crossed. These results are consistent with the existence of Kondo like bound states of the U$^{4+}$ ionic configurations and the conduction electrons. Below the transition, these configurations are split by the development of quadrupolar ordering. The peak separation can be interpreted as a direct measurement of the order parameter. Measurements on a policrystalline UAu_2Si_2$ sample are also reported, with a comparative study of the behavior of both materials.Comment: 4 pages (Latex) + 2 postscript figure

3D structure design of magnetic ferrite cores using gelcasting and pressure-less sintering process

Gelcasting is a well established process for ceramics manufacturing which recently has been proved to be successful for soft ferrites as well. This approach is particularly interesting for power electronics application in which the magnetic components (e.g. transformers and inductors) are three dimensionally integrated on the power module substrate. This paper proposes a gelcasting process adapted to make it more effective for 3D heterogeneous integration. The main novelties in this direction consist of low solid load (65wt%) and gelation without catalyst to improve casting and de-airing steps. The magnetic properties of gelcast samples are compared with commercial materials and correlated with the microstructure