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Mater Sci Nanotechnol 2017
Volume 1 Issue 3
Magnetic Materials 2017
Page 82
October 09-10, 2017 London, UK
International Conference on
Influence of carbon impurity on the magnetic
properties of the EuB
6
T S Altshuler, Yu V Goryunov, A N Levchenko
1
and
V B Filippov
1
Kazan E K Zavoisky Physical-Technical Institute, Russia
1
Institute of Applied Physics, Academy of Science of Moldova, Republic of
Moldova
E
uB
6
is a well-known compound with a colossal
magnetoresistance. Its electronic and magnetic properties
depend on each other. The influence of carbon doping in the
anion sublattice EuB
6-х
С
х
on the magnetic properties of this
compound was studied by electron spin resonance (ESR)
and by electron transport (ET). The ESR measurements were
performed at 9.3 GHz in the temperature range T = 10-300
K, and ET measurements in the temperature range 80-300
K. According to the ESR data, magnetic phase separation
is observed for all the samples. The observed two ESR lines
correspond to two types of polarons, in which there is a
Кondo and an anti-Кondo coupling of the magnetic moments
of Eu
2+
with the magnetic moments of the charge carriers. At
x= 0.02 the splitting of the ESR line is observed at 40K as well
as EuB
6
. However, in EuB
5.93
C
0.07
the ESR line splits already
at 130 K. At high temperatures, we observe linear resistance
R (T) temperature dependencies for all samples that are
characteristic for metals. The concentration dependence of
the residual resistance R0 is shown in the figure. For a sample
with x=0.07 at temperatures below 130 K, R(T) acquires a
semiconductor character, which is probably related to the
opening of a gap in the spectrum of electronic excitations
due to either stronger localization of electrons or changes
in the Fermi surface. The dependence R (T) resembles the
temperature dependence of the width of the ESR line of this
sample. This similarity suggests that both dependencies are
due to the same dissipative processes in the systems of localized
magnetic moments and current carriers. It is obvious that the
tetravalent carbon, penetrating the sub lattice of the trivalent
boron, must be an electron donor. In accordance with this,
it must increase the concentration of electrons in the sample
and, of course, its conductivity. However, the opposite result
is observed. Perhaps this is due to the increase in the number
of scattering centers in the boron sublattice. A key role in the
relaxation of the electronic subsystems of EuB
6-х
С
х
can be
due to specific mechanisms associated, for example, with s-f
Hubbard-Mott scattering and s-f super-exchange of localized
f-electrons through the valence band electrons.
taltshuler@yandexl.ruMaterials Science and Nanotechnology