The intrinsic radiation and electromagnetic wave reflection coefficient
in the range of 8 mm of
Ni 2,14Mn0,81GaFe0,05
and
Ti-Ni
alloys in the temperature interval near the phase transitions of the 1st
and 2nd order
I. V. Bychkov1, V. A. Golunov2, D. S. Kalenov2,
A. P. Kamantsev2, D. S. Kuchin2, V. V. Koledov2,
D. A. Kuzmin1, V. V. Meriacri2, S. V. von
Gratowski 2,
M.
P. Parkhomenko2, A. V. Mashirov2, V. G. Shavrov2
1Chelyabinsk
State University,
2Kotelnikov
Institute of Radio-engineering and Electronics of RAS
The paper is received on December 1, 2014
Abstract. The original experimental
techniques are created for the study of the electromagnetic response and
spontaneous radiation of electromagnetic waves in the range of 28-32 GHz, of samples
of the alloys with phase transitions (PT). Using these techniques, the
following experiments were done: there were carried in situ measurements
of the electromagnetic waves radiation of a ferromagnetic Heusler alloy Ni2,14Mn0,81GaFe0,05
by radiometry techniques (in the range of 28-32 GHz), and simultaneously
measuring of the low-frequency magnetic susceptibility, reflecting the
occurrence of magnetic and structural PTs in the sample. An anomalous no
monotonic temperature dependences of the radiation in the temperature range
near magneto structural PT of the 1st order (330 - 345 K), and abnormal
fluctuations in the radiation near the Curie point (360 K) were detected. The
contributions to the signal from the self-radiation of the sample and the
reflected electromagnetic radiation from a background were separated. The
influence of the nature of the kinetics of PT upon millimeter wave radiation of
sample was investigated by changing the rate of heating / cooling from 0.1 K /
s to 10 K / s. It was shown that the peaks of the intrinsic radiation increases
with the rate of temperature change. These methods confirm that the detected
anomalies are not subjected to Planck's formula and the Stefan-Boltzmann law
and are associated with non-equilibrium processes at PT. The study by the
radiometric technique of the electromagnetic radiation of the TiNi alloy of
it’s intrinsic radiation and electromagnetic wave reflection coefficient in the
range of 28-32 GHz were done. In the temperature range near the thermoelastic martensitic
structural PT (290-315 K) there were revealed the anomalies of the intrinsic
radiation and the reflection coefficient which are associated with the
non-equilibrium processes at PT. The model is propose that relates the
reflection coefficient anomalies and intensity of intrinsic radiation. The results
of numerical simulations are in good qualitative agreement with the
experimental data.
Keywords: electromagnetic waves, millimeter range, phase transition,
shape momery effect, TiNi, Heusler alloys, reflection coefficient, intrinsic
radiation, evanescent modes.
|