Page 154 - 00. Complete Version - Progress Report IPEN 2014-2016

154 Nuclear Science and Technology | Progress Report

Materials which have been investigated are:

1 Oxide semiconductors: new families of semiconductors, which

are doped with magnetic materials in order to use the elec-
tron spin information, are under intensive investigation as
they can be used for spintronics. Effects of doping in ZnO,
In2O3, SnO2, TiO2, and vanadium oxides are being investigat-
ed by PAC in order to understand the local crystalline struc-
ture around the dopant and the its electronic structure.

2 Insulator oxides with large bandgap as HfO2, ZrO2 and CeO2
are promising materials to replace SiO2 as a gate dielectric to
prevent leakage current in complementary metal oxide semi-
conductor (CMOS) transistors. Thin films and nano-struc-
tured powders of these materials are under investigation using
PAC spectroscopy in order to obtain an atomic scale charac-
terization of their properties under different temperatures.

3 Rare-earth based compounds: series of intermetallic compounds
based on rare earth elements show different magnetic behaviors
and exhibit very interesting physical phenomena like Fermi liquid
behavior, Kondo effect, etc. These properties are not well under-
stood yet, and nuclear techniques are very suitable to investigate
the microscopic origin of such phenomena. In our laboratory, we
have studied heavy fermions compounds such as REIn3 (RE = ra-
re-earth element), REMn2X2(RE= rare-earth, X = Si, Ge) and LaMn-
Si2 with PAC technique using 140Ce and 111Cd probe nuclei.

Fig 3. (left) Pencil-like particles of ZnO doped with Cr (M. R. Cordeiro, Ph.D. Thesis, IPEN, 2012). (Center) ZnO microtube decorated with
nanowires on the surface (C. M. Rivaldo-Gómez et al. Scientific Reports 5, 15128, 2015). (right) Electron back scattering diffraction
image showing the spatial distribution of Fe and Hf in Fe doped HfO2 (T. S. N. Sales et al. AIP Advances 7, 056315, 2017).

4 Magnetic nanoparticles of Fe3O4 and XFe2O4 (X = Mn,
Co, Ni) with sizes homogeneously smaller than 30 nm

Instituto de Pesquisas Energéticas e Nucleares