Abstracts Book - IMRC 2018

• SD1-P015
TUNNELING I-V CHARACTERISTICS FOR A SUPERCONDUCTOR-
INSULATOR-HALF-METAL JUNCTION
Alfredo Mamian Mamian 1 , Jesus Heiras 2 , Gilberto Bolaños 1
1 Universidad del Cauca, Laboratorio de Fisica de Bajas Temperaturas, Departamento de
Ingenieria Fisica, Colombia. 2 Universidad Nacional Autónoma de México, Centro de
Nanociencias y Nanotecnologia, Mexico.
Half-metals, HM, are compounds with a 100% spin polarization in one direction:
they are metallic for one spin direction but insulators, or semiconductors, for the
other direction. From the viewpoint of the density of states (DOS) it is finite at the
Fermi level for one spin direction and zero, or negligible small, for the other.
Therefore, there is a band gap for one the spin direction. Experimentally it has been
observed CrO2 exhibits a polarization greater than 97% at 4K, which makes it a
strong candidate for spin valves and other spintronic devices including sensors and
magneto optical reading and writing data storage devices. The significant advances
recently made in the fabrication of thin films, as well as in the development of new
and more efficient theoretical simulations for studying solids have reactivated the
research in half-metals in themselves and the studies in the development of devices
that use their properties. In this work the current vs. voltage characteristics, I-V, for
a Superconductor-I-Half-metal (SIHM) have been calculated with a simple and
straightforward procedure. It essentially involves a product of the corresponding
DOS for both electrodes of the junction at a given voltage, taking into account the
proper values for the Fermi function (at T = 0 K). CrO2 and a hypothetical BCS
superconductor have been used as electrodes separated by a perfect insulator to
form the tunnel junction. The DOS for the half-metal has been digitized to include
all the details in the calculation. The equation used to evaluate the current at each
voltage is:
which gives the current for electrons striking the junction with an energy Ex and with
total energy Et, D(Ex,Et) is the transmission coefficient, f(E) the Fermi-Dirac
distribution function and ρ(E) is the density of states for electrodes 1 and 2. It is
shown that the results for IV obtained reveal important aspects of the properties of
half-metals when certain conditions are imposed on the tunneling current.
Keywords: Tunnel junction, Half metals, Density of states
Presenting authors email: amamianm@unicauca.edu.co