Electronic and magnetic properties of ordered and disordered binary alloy ni-al
Date
2019
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Faculty of Physics
Abstract
The order-disorder always exist in materials. The structural, electronic and magnetic
properties of metals and metallic alloys have been the subject of intense research due to
their applications in many technological purpose. Inter-metallic binary alloys of Ni and
Al has attracted much attention in the field of science and technology because of their
use in computer chips, variety of turbine components, medical implants and commercial
applications etc. Magnetic properties and properties based on electronic structure of
ordered alloys NiAl and Ni
Al have been investigated using the first-principles study
based on density functional theory and density functional perturbation theory. In order
to understand the electronic properties, we have performed electronic band structure
calculations. Our findings show that all the systems considered are metallic in nature.
To know the contributions of the orbitals in the bands, the system is analyzed via fat
bands which reveals most of the contributions on valence band of NiAl and Ni
3
Al is
due to d-orbital and the contributions on conduction band is due to s and p-orbitals.
Furthermore, spin up and spin down calculations have been done to know the magnetic
properties of the system. Our calculations also suggest the magnetic nature of Ni
Al
and non-magnetic nature of NiAl. It has been found that the magnetic moment of alloys
containing Ni and Al increases with increasing Ni concentration. The study of Ni
Al is
of great interest from magnetic point of view as it has magnetic moment 0.52
. The
value of magnetic moment of NiAl and Ni
Al obtained in the present work agrees with
previous studies. From the study of liquid state of Ni-Al, it is found that the NiAl melt
at 1873 K is ordering in nature which doesn’t support de-mixing in the solid form.
3
In studying vibrational properties, phonon modes in Ni
Al are observed via phonon
dispersion relation, which is di erent than that from NiAl. Optical branches gets more
uniformly shifted in frequency in Ni
3
3
Al than in NiAl. Optical phonons have a non-zero
frequency at the center of Brillouin zone and show no dispersion near that long wavelength
limit. Modes are originated from electronic bands resulting to mode gap of 1.56
THz in NiAl and reduces the gap while increasing nickel content. Optical properties are
analyzed through the calculations of dielectric function, reflectivity and refractive index.
The maximum number of free electrons near the Fermi level in NiAl are responsible to
change its reflectivity.
Description
Keywords
magnetic properties, magnetic nature