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A.M. AlievA.G. Gamzatov A.B. BatdalovA.S. Mankevich I.E. Korsakov 《Physica B: Condensed Matter》2011,406(4):885-889
A technology of obtaining the single-phase ceramic samples of La1−xKxMnO3 manganites and the dependence of their structural parameters on the content of potassium has been described. Magnetocaloric effect (MCE) in the obtained samples has been measured by two independent methods: classical direct methodic and a method of magnetic field modulation. The values of MCE obtained by both methods substantially differ. The explanation of the observed divergences is given. The correlation between the level of doping and MCE value has been defined. The value of TC determined by the MCE maximum conforms with the literature data obtained by other methods. 相似文献
2.
A. M. Aliev A. G. Gamzatov A. B. Batdalov A. S. Mankevich I. E. Korsakov 《Journal of Experimental and Theoretical Physics》2011,112(3):460-468
A technology for obtaining single-phase ceramic samples of La1 − x
K
x
MnO3 manganites, as well as the dependence of their structure parameters on the potassium content, is described. The magnetocaloric
effect in the samples has been measured by two direct methods, the classical method and the magnetic field modulation method,
and has been calculated from the specific heat data. The values of the magnetocaloric effect obtained by these methods are
significantly different. The observed discrepancies have been explained. Correlation between the doping level and the value
of the effect has been found. It has been shown that the magnetic-field dependence of variation of the magnetic entropy near
T
C in weak fields corresponds to theoretical calculations and that the value of the magnetocaloric effect in high magnetic fields
can be predicted using this dependence. 相似文献
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4.
The temperature and magnetic-field dependences of the magnetocaloric effect in manganites La1−x
Ag
x
MnO3 (x = 0.1; 0.15; 0.2) and La1−x
K
x
MnO3 (x = 0.1; 0.11; 0.13; 0.15; 0.175) were studied by a direct method. Large changes in the sample temperature were detected as
a magnetic field changed by ΔH = 10 kOe. Temperatures of the magnetocaloric effect maxima are near room temperatures. Field dependences of the magnetocaloric
effect show no signs of saturation in fields to 30 kOe. 相似文献
5.
A. G. Gamzatov A. M. Aliev K. Sh. Khizriev I. K. Kamilov A. S. Mankevich I. E. Korsakov 《Physics of the Solid State》2011,53(11):2271-2274
The heat capacity of the manganite La0.87K0.13MnO3 has been measured in the temperature range 80–350 K. The nature of the ferromagnetic phase transition and the critical properties
of heat capacity near the Curie temperature have been studied. The regularities of variations in the universal critical parameters
near the phase transition point have been established. The calculated critical exponent and amplitudes of the heat capacity
with allowance for corrections on the scaling (α = −0.13 and A
+/A
− = 1.178) correspond to the critical behavior of the 3D Heizenberg model. 相似文献
6.
I. K. Kamilov A. G. Gamzatov A. B. Batdalov A. S. Mankevich I. E. Korsakov 《Physics of the Solid State》2010,52(4):789-793
The magnetocaloric effect and the heat capacity of La1 − x
K
x
MnO3 (x = 0.1, 0.15, 0.175) ceramic samples have been studied at temperatures in the range 77–350 K and in magnetic fields of up
to 27 kOe. The technique for preparing the samples has been described. The heat capacity anomalies related to the ferromagnetic-paramagnetic
magnetic phase transition have been revealed and interpreted. It has been demonstrated that the change in the magnetic entropy
ΔS calculated from the data on the heat capacity C
p
and direct measurements of the magnetocaloric effect ΔT reaches values that are of practical interest. 相似文献
7.
Yu. F. Kutaev S. K. Mankevich O. Yu. Nosach E. P. Orlov 《Journal of Russian Laser Research》2002,23(3):235-251
The effect of a wide-range background exposure on the sensitivity of a laser receiver with an iodine quantum filter ( =1.315 m) is theoretically investigated. The sensitivity of the laser receiver is shown to be only about 12% less than the quantum limit when detecting optical signals against the background of the solar disk. It is also shown that in the case where the radiance temperature of a blackbody considered as a source of background radiation is 1.6· 104 K, a twofold decrease in the sensitivity of the laser receiver is expected. The sensitivity of the receiver discussed is compared with that of a receiver with a visible-range photomultiplier tube. In the case of detection of optical signals against the background of the solar disk, the sensitivity of a receiver with an FEU-115 photomultiplier tube and interference filter ( 5 nm) is approximately 400 photons when the signal-to-noise ratio of the receiver is equal to unity. 相似文献
8.
9.
Gamzatov A. G. Batdalov A. B. Khanov L. N. Mankevich A. S. Korsakov I. E. Kaul’ A. R. 《Physics of the Solid State》2012,54(3):617-621
Results of investigation of resistivity and magnetoresistance of manganites La1 − x
K
x
MnO3 (x = 0.050–0.175) are presented. Behavior of resistivity ρ(T) in the paramagnetic and ferromagnetic phases has been described. To describe ρ(T) near the phase-transition temperature, notions of the percolation theory have been used. Two maxima have been found in the
dependence ρ(T); their appearance has been attributed to the ceramic nature of the studied samples. The observed increase in magnetoresistance
with a decrease in temperature is caused by intergranular spin-polarized tunneling of charge carriers. 相似文献
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