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1
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Ab Initio Study of Electronic and Magnetic Structure and Structural Phase Transition of (Fe_{1 - x}Mn_{x})_2P_{1 - y}Ge_{y} Alloys

100%
Deniszczyk J., Woźniakowski A., Kolano R., Kolano-Burian A.
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EN
The paper presents results of the ab initio electronic structure calculations performed for the (Fe_{0.5}Mn_{0.5})_2P_{0.67}Ge_{0.33} alloy, a member of (Fe_{1 - x}Mn_{x})_2P_{1 - y}Ge_{y} family of alloys showing a giant magnetocaloric effect. Calculations confirmed the strong relationship between the magnetic state and crystal structure of the alloy. To investigate the isostructural phase transition driven by external magnetic field observed in (Fe_{0.9}Mn_{1.1})P_{0.8}Ge_{0.2} we utilized the fixed spin moment approach. Total energy analysis confirmed the occurrence of isostructural phase transition.
2
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Giant Magnetocaloric Effect in Manganites

88%
Szymczak R., Kolano R., Kolano-Burian A., Dyakonov V., Szymczak H.
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issue 1
203-206
EN
In this review we briefly discuss the magnetocaloric properties of the manganites. It is evidenced that the maximum entropy change observed in manganites exceeds that of gadolinium (the prototype material for room temperature refrigerators). For the manganites characterized by second-order magnetic phase transitions the scaling hypothesis is discussed. It is shown that simple phenomenological model with only one fitting parameter, presented in this paper, satisfactorily describes experimental observations.
3
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Dynamic Magnetic Properties of the Magnetostrictive Rapidly-Quenched Alloys

88%
Kolano R., Kolano-Burian A., Szynowski J., Polak M., Steczkowska-Kempka M.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
131-134
EN
This work was aimed at investigating the FeNbCuSiB and FeNiMoB type alloys exhibiting relatively high saturation magnetostriction after suitable heat treatment, which makes them suitable for application in force sensors. Samples of both alloys were prepared in a form of toroidal cores wound from amorphous ribbons obtained by melt-spinning, and then the cores were annealed under longitudinal and transverse magnetic field. An effect of the induced magnetic anisotropy and of the applied compressive stresses on the dynamic magnetic properties of both alloys within a frequency range from 50 Hz to 50 kHz was studied.
4
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New Method of Measurement of the Magnetoelastic Characteristics for Tensile Stresses

88%
Salach J., Szewczyk R., Bieńkowski A., Kolano-Burian A., Falkowski M.
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issue 5
775-777
EN
The paper presents a novel method of measurements of tensile stress dependence of the magnetic characteristics of ring-shaped cores made of soft amorphous alloys. In the presented method, the uniform tensile stress was applied perpendicularly to the magnetizing field direction. Magnetoelastic core with closed magnetic circuit was fixed on the non-magnetic backings enabling the conversion of compressive force into tensile stresses as well as it enables the core to be winded by magnetizing and sensing windings. Magnetoelastic characteristics measured under tensile stress, for Fe_{25}Ni_{55}Si_{10}B_{10} alloy annealed in temperature 350°C for 1 h, are presented in this paper. The presented results indicate high tensile stress sensitivity of Fe_{25}Ni_{55}Si_{10}B_{10} alloy. Moreover, together with magnetoelastic characteristics for compressive stresses (presented previously in the literature), the describes results create possibility of further development of models of the magnetoelastic effects in amorphous alloys.
5
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Magnetocaloric Cooling Device with Reciprocating Motion of the Magnetic Field Source

76%
Kolano R., Kolano-Burian A., Hreczka M., Polak M., Szynowski J., Tomaka W.
Acta Physica Polonica A
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2016
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vol. 129
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issue 6
1205-1209
EN
This paper describes the magnetic cooling device model designed and built at the Institute of Non-Ferrous Metals in Gliwice, which utilizes reciprocating motion of a magnetic field source and a cyclic flow of a coolant through regenerator. The regenerator made from gadolinum made it possible to obtain an adiabatic temperature change of 2.5 K at the magnetic field of 0.8 T. The magnetic field source was built using neodymium magnets according to our own technology. For the heat transfer, a liquid having the specific heat of about 4000 J/(kg K) has been applied. We have also developed and applied a special driving system enabling reciprocating motion of the magnetic field source and of the pistons in the hot and cold heat exchangers. The tests were made with this cooling model showing that it was possible to obtain, at the frequency of 0.5 Hz, the liquid temperature gradient of 4 K. The potential energy savings resulting from application of this device have been evaluated and compared with the literature data presenting a pre-industrial prototype of the magnetic refrigerator utilizing similar solutions to those applied in our cooling model.
6
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Magnetic and Structural Study of Mn_{1.15}Fe_{0.85}P_{1-x}Ge_{x} (0.25 < x < 0.32) Magnetocaloric Compounds Prepared by Arc Melting

64%
Hawelek L., Wlodarczyk P., Zackiewicz P., Polak M., Kaminska M., Puźniak R., Radelytskyi I., Kolano-Burian A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 1
76-80
EN
Recently, room temperature magnetocaloric materials increasingly attracted attention in the development of magnetic refrigerators. In this paper, an effect of P/Ge substitution on the magnetic phase transition in the series of Mn_{1.15}Fe_{0.85}P_{1-x}Ge_{x} (0.25 < x < 0.32) magnetocaloric compounds prepared by the arc melting technique and subsequent homogenization process has been studied. Calorimetric and magnetization results show that the temperature of structural phase transition coincide with the Curie temperature and fall within the temperature range 270-355 K. The magnetic entropy change reaches the maximum value for the compound with x=0.28 and equals to 32 J/(kg K) for the magnetic field change of 5 T. The adiabatic temperature change for the same sample, measured using magnetocalorimeter, is equal to 1.2 K for the magnetic field change of 1.7 T. It was found that the increase of Ge content in the sample causes weakening of first order magnetic transition, which is manifested by the lowering difference in transition temperature measured in two zero-field-cooling and field-cooled-cooling regimes.
7
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Origin of Magnetic Anisotropy of Gd_{5}Si_{2}Ge_{2} Compound

64%
Szymczak R., Kolano R., Kolano-Burian A., Hawelek L., Krzymanska B., Aleshkevich P., Dyakonov V., Szymczak H.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1261-1262
EN
The second-order anisotropy constant K_2 in polycrystalline Gd_5Si_2Ge_2 giant magnetocaloric material was measured as a function of temperature by the modified singular point detection technique. Although the structural, electrical, thermal, magnetic and magnetocaloric properties of the Gd_5Si_2Ge_2 have been rather well investigated experimentally, magnetic anisotropy of this system is almost unknown. The singularity indicating the anisotropy field was determined analyzing ac susceptibility data taking into account several features of the magnetization curve. The temperature dependence of the anisotropy fields was measured from 4.2 K up to the Curie temperature. The observed relationship between K_2 (T)/K_2 (0) and magnetization M (T)/M (0) was explained assuming dipolar origin of magnetic anisotropy of Gd_5Si_2Ge_2 compound.
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