CC BY
15
Chelyabinsk Physical and Mathematical Journal. 2020. Vol. 5, iss. 4, part 2. P. 635-642.
DOI: 10.47475/2500-0101-2020-15423
SCALING MAGNETIC AND MAGNETOCALORIC PROPERTIES OF GdAl2 BY ERBIUM SUBSTITUTION
S. Taskaev1'2'3'", V. Khovaylo2'3, M. Ulyanov1'4, D. Bataev1, A. Basharova1, M. Kononova1'3, D. Plakhotskiy1, M. Bogush1, M. Gavrilova1, D. Zherebtsov2, Z. Hu5
1 Chelyabinsk State University, Chelyabinsk, Russia
2South Ural State University (National Research University), Chelyabinsk, Russia 3National University of Science and Technology «MISiS», Moscow, Russia 4Immanuel Kant Baltic Federal University, Kaliningrad, Russia 5 University of Science and Technology Beijing, Beijing, P. R. China. atsv@csu.ru
We report on magnetic and magnetocaloric properties of polycrystalline Gd100_xErxAl2 (x = 0; 50). It was found that substitution of Gd for Er does not affect considerably the value of the isothermal magnetic entropy change, which is equal to ASM = -5.0 J/(kgxK) at Tc = 163 K for GdAl2 and ASm = -4.9 J/(kgxK) at Tc = 97 K for Gdo.sEro.5Ah (for the magnetic field change of 3 T). However, in the Gd0.5Er0.5Al2 alloy, a large MCE is observed in a wide temperature range AT = 66 K, which makes this materials promising for a magnetic cooling technology at low temperatures.
Keywords: magnetocaloric effect, magnetic cooling, Laves phase, natural gas liquefaction, ferromagnet, rare-earth element.
Introduction
Progress in the materials science and the solid state physics makes it possible to improve the existing and create new devices and technologies that have fundamentally better properties than their predecessors. For example, existing refrigeration plants consume approximately 20% of the total electricity generated over the world. This suggests that conventional refrigeration systems equipped with a compressor are economically ineffective. Therefore, there is a need for a fundamentally new cooling technology that will allow one to change a temperature of objects in a wide range, down to the cryogenic region. One of such technologies is the magnetic cooling technology based on the magnetocaloric effect (MCE) [1]. One of the most perspective areas for an application of the magnetic cooling technology in industry is the liquefaction of the natural gas. Temperatures at which the state of aggregation changes from gaseous to liquid are in the cryogenic temperature range. Since a magnetic cooling device must be suitable for liquefying various gases, materials with a wide operating range are required as a working fluid.
The Laves phase materials (RM2; R is a rare earth element and M is a transition metal) have been considered as one of the best candidates for a magnetic cooling technology. In the last decades, these materials have been widely studied as functional materials, for example, as the superconducting magnets [2] and the materials for
This work was financially supported by Russian Science Foundation grant no. 18-42-06201.
hydrogen storage [3]. A representative of the Laves phase, the GdAl2 intermetallic compound, has been intensively studied by a variety of experimental techniques, including the Mossbauer spectroscopy [4], the nuclear magnetic resonance [5], the Compton scattering [6], etc. Magnetic properties of the polycrystalline GdAl2 have been successfully explained in the framework of the Rudermann — Kittel — Kauya — Yoshida model which predicted the Curie temperature for this compound to be TC = 170 K, i. e., in the excellent agreement with the experimental value [7]. The influence of the substitution of Al sites and Gd sites on magnetic and magnetocaloric properties has been studied for Gd(FexAli_x)2 [8], Gd(CoxAli_x)2 [9], Gdi_yTbyAl2 [10], and Gdi_yHoyAl2 [11] systems. Magnetocaloric properties of the undoped GdAl2 have been reported in a number of works [12-14]. Results of these studies have indicated that MCE in GdAl2 depends both on alloying and the structural state. Specifically, MCE in the nanocrystalline or nanostructured GdAl2 is generally lower than that reported for polycrystals [12-14]. The substitution of Gd sites by Tb resulted in a decrease of the Curie temperature down to 100 K in TbAl2 and a slight increase in the magnitude of the maximal value of the isothermal magnetic entropy change [10]. In the Gd1-yHoyAl2 system, the magnetic transition temperature decreased down to 29 K in HoAl2, the magnetic entropy change was not reported [11]. In the present work, we report on magnetic and magnetocaloric properties of the polycrystalline samples of GdAl2 and Gd0.5Er0.5Al2.
Samples preparation and Measurements
The studied polycrystalline samples Gd100_xErxAl2 (x = 0; 50) were synthesized by argon-arc melting from the initial high-purity chemical elements Gd, Er, and Al with a purity of at least 99.98 at%. The synthesized samples were turned over and re-melted at least three times in order to achieve a better homogeneity. The elemental analysis was performed using the energy dispersive X-ray fluorescence spectroscopy by JEOL 7001 electron microscope setup. X-ray diffraction and X-ray phase analyzes were performed on a Rigaku Ultima V X-ray diffractometer using Cu-Ka radiation. The scanning electron microscopy was carried out using a JEOL 7001 electron microscope. All magnetic measurements were carried out using Physical Properties Measurements Systems and Quantum Design Versa Lab magnetometers according to standard measurement procedures at temperatures up to 350 K in magnetic fields up to 3 T.
Results and Discussion
Table 1
Results of X-ray pattern approximation by the Rietveld refinement method in Rikagu PDXL software.
Phase Compound wt% a, A
GdAl2
Gd-Al 1:2 (cubic) GdAl2 99.4 7.8988
Gd oxide (cubic) Gd2Ü3 0.62 10.733
Gd0.5Er0.5Al2
Gd-Al 1:2 (cubic) GdAl2 99.3 7.8467
Gd oxide (cubic) Gd2Ü3 0.72 10.592
other undefined phase (see Table 1)
The results of the structural and phase analyzes of the obtained compounds Gd100_xErxAl2 (x = 0; 50) are shown in Figs. 1 and 2. It is clearly seen that for both the compositions peaks of the diffraction profiles are sharp; hence, the samples are well crystallized and homogeneous. The alloys GdAl2 and Gd0.5Er0.5Al2 contain the main phase, a small amount of an impurity oxide Gd2O3, and <1% of
40 60
2©, deg.
Fig. 1. X-ray diffraction pattern of GdAl2 measured at room temperature
Fig. 2. X-ray diffraction pattern of Gd0.5Er0.5Al2 measured at room temperature
The results of the scanning electron microscopy (see Figs. 3 and 4) show an almost uniform contrast, which corresponds to a single-phase sample, for GdAl2, and an inhomogeneous contrast for Gd0.5Er0.5Al2, but the amount of impurity phases is not large and does not exceed 5%. Based on the data of the energy dispersive spectroscopy, the weight content of elements in the studied alloys Gdi00-xErxAl2 (x = 0; 50) is Gd — 68.39 wt% and Al — 31.61 wt% for GdAl2 and Gd — 34.49 wt%, Er — 32.78 wt% and Al — 32.73 wt% for Gd0 5Er0 5Ak.
Fig. 3. Scanning electron microscopy image of the GdAl2 alloy
Fig. 4. Scanning electron microscopy image of the Gdo.sEr0.5 Al2 alloy
1,5 2,0
Fig. 5. Magnetic field dependences of magnetization of GdAl2
1,5 2,0 Mo
Fig. 6. Magnetic field dependences of magnetization of Gd0.5Er0 5 Al2
200 150 100 50 0
§ -50
-100 -150 -200
E <
. GdAI2 ; 7~= 50 K
: J
0
[i0H, T
200 150 100 50 0 -50 -100 -150 -200
--
: J Gd0.5Er0.5AI2 " 7~= 50 K -
0
1
\i0H, T
Fig. 8. Magnetic hysteresis loop of Gd0.5Er0.5Al2 at T =50 K
Fig. 7. Magnetic hysteresis loop of GdAl2 at T =50 K
Shown in Figs. 5-12 are results of the magnetic measurements of Gd100_xErxAl2 (x = 0; 50). In Figs. 5 and 6 one can find the field dependences of the magnetization of the GdAl2 and Gd0.5Er0 5Al2 compounds obtained in a temperature range 50-300 K. Note that for the samples under study the magnetization saturates in fields of about 0.3 T, and the saturation magnetization Ms for Gd0.5Er0 5Al2 is lower than 25%.
The hysteresis loops measured at a temperature of T = 50 K show that the alloys are soft magnetic materials and do not have any significant coercive force (Figs. 7, 8). At room temperatures the Gd100_xErxAl2 (x = 0; 50) alloys are paramagnets. The
temperature of the ferromagnetic-paramagnetic phase transition was determined from the Belov — Arrot curves (Figs. 9 and 10) and was found to be equal TC = 163 K for GdAl2 and TC = 97 K for Gd0.5Er0.5Al2.
Fig. 9. Belov — Arrot plot of GdAl2 Fig. 10. Belov-Arrot plot of Gdo.5Ero.5Al2
The temperature dependences of the change in the magnetic part of the entropy calculated from the magnetic measurements data are shown in Figs. 11 and 12. The calculation was made for external magnetic fields up to 3 T for comparison with the literature data. Our calculations showed that for the GdAl2 and Gd0.5Er0 5Al2 alloys, the isothermal change in magnetic entropy is ASM = -5.0 J/(kgxK) and ASM = -4.9 J/(kgxK) in fields up to 3 T, respectively. Thus, as a result of the research, it was found that when Gd is replaced by Er atoms in a concentration of up to 50%, the Gd100-xErxAl2 (x = 0; 50) alloy system has almost the same MCE value but in a wide temperature range AT = 66 K.
O)
5 3
CO
<
1 1 1 - GdAI2 i ■ i —•— [10H=3T
Ho"=2T .
- —•—H0H=1T -
i . i i . i
140
160
180
200
7, K
Fig. 11. Magnetic entropy change of GdAl2 for external magnetic field change up to 3T
Fig. 12. Magnetic entropy change of Gd0.5Er0.5 Al2 for external magnetic field change up to 3T
Conclusions
Our studies have shown that the Laves phase compounds Gd100-xErxAl2 (x = 0; 50) are promising materials for the technology of magnetic cooling at low temperatures with a high MCE value in a wide temperature range AT = 66 K. Taking into account that the temperature of the liquefaction of methane (CH4) is 113 K, and that of ethane (C2H6) is 184 K, the region of the magnetocaloric effect of the studied compounds Gd100-xErx Al2 (x = 0; 50) is in a close proximity to these values, and these intermetallic compounds,
having a high specific magnetic moment and a reversible second-order magnetic phase transitions, can be one of the real candidates for the magnetocloric liquefaction of natural gases.
References
1. GutfleischO., Gottschall T., Fries M., BenkeD., RadulovI., SkokovK.P., WendeH., GrunerM., AcetM., EntelP., FarleM. Mastering hysteresis in magnetocaloric materials, Philosophical Transactions of the Royal Society A, 2016, vol. 374, p. 20150308.
2. ChuF., ChenZ., Fuller C.J., LinC.L., MihalisinT. Superconductivity and structural transformation in HfV2 and Nd-doped HfV2. Journal of Applied Physics, 1996, vol. 79, pp. 6405-6407.
3. AokiK., LiX.G., MasumotoT. Differential thermal analysis of hydrogen-induced amorphization in C15 laves phase GdFe2. Acta Metallurgica et Materialia, 1992, vol. 40, pp. 221-227.
4. PresaP., ForkerM.,. Cavalcante J.Th., AyalaA.P. Spin and temperature dependence of the magnetic hyperfine field of 111Cd in the rare earth-aluminum Laves phase compounds RAl2. Journal of Magnetism and Magnetic Materials, 2006, vol. 306, pp. 292-297.
5. TozoniJ.R., Teles J., AuccaiseR., Oliveira-Silva R., Rivera-Ascona C., Vidoto E.L.G., Guimarres A.P., Oliveira I.S., Bonagamba T.J. Multi-quantum
echoes in GdAl2 zero-field high-resolution NMR. Journal of Magnetic Resonance, 2011, vol. 212, pp. 265-273.
6. SahariyaJ., MundH.S., AhujaB.L. Electronic properties of the magnetocaloric compound GdAl2: A Compton scattering study. Journal of Physics and Chemistry of Solids, 2011, vol. 72, pp. 1515-1518.
7. Williams D.S., ShandP.M., PekarekT.M., SkomskiR., PetkovV., Leslie-Pelecky D.L. Magnetic transitions in disordered GdAl2. Physical Review B, 2003, vol. 68, p. 214404.
8. XiongD.K., LiD., LiuW., Zhang Zh. Magnetocaloric effect of Gd(FexAl1-x)2 compounds. Physica B: Condensed Matter, 2005, vol. 369, pp. 273-277.
9. FuH., HadimaniR.L., MaZ., WangM.X., TengB.H., JilesD.C. Magnetocaloric effect in GdCoxAl2-x system for (0.15 < x < 1) compositions. Journal of Applied Physics, 2014, vol. 115, p. 17A914.
10. Ribeiro P.O., Alho B.P., Alvarenga T.S.T., ^bregaE^., Magnus A., CarvalhoG., SousaV.S.R., CaldasA., OliveiraN.A., RankeP.J. Theoretical investigations on the magnetocaloric and barocaloric effects in TbyGd1-yAl2 series. Journal of Alloys and Compounds, 2013, vol. 563, pp. 242-248.
11. SousaV.S.R., SilvaL.E.L., Gomes A.M., RankeP.J. Spin reorientations and crystal field modification in Ho1-yGdyAl2 compounds. Journal of Alloys and Compounds, 2016, vol. 686, pp. 522-525.
12. MaS., LiW.F., LiD., XiongD.K., SunN.K., GengD.Y., LiuW., ZhangZ.D.
Large cryogenic magnetocaloric effect in the blocking state of GdAl2/Al2O3 nanocapsules. Physical Review B, 2007, vol. 76, p. 144404.
13. PaulaV.G., SilvaL.M., Santos A.O., LangR., OtuboL., CoelhoA.A., Cardoso L.P. Magnetocaloric effect and evidence of superparamagnetism in GdAl2 nanocrystallites: A magnetic-structural correlation. Physical Review B, 2006, vol. 93, p. 094427.
14. PrustyM.M., Chelvane J.A., NirmalaR. Magnetism and magnetocaloric effect of melt-spun, nanostructured GdAl2. Materials Research Express, 2020, vol. 7, p. 064001.
Accepted article received 12.09.2020. Corrections received 04.11.2020.
Челябинский физико-математический журнал. 2020. Т. 5, вып. 4, ч. 2. С. 635-642.
УДК 537.638.5 Б01: 10.47475/2500-0101-2020-15423
МАСШТАБИРОВАНИЕ МАГНИТНЫХ
и магнитокалорических свойств сал12
ЗАМЕЩЕНИЕМ ЭРБИЯ
С. Таскаев1'2'3'", В. Ховайло2'3, М. Ульянов14, Д. Батаев1, А. Башарова1, М. Кононова1'3, Д. Плахотский1, М. Богуш1, М. Гаврилова1, Д. Жеребцов2, Д. Ху5
1 Челябинский государственный университет, Челябинск, Россия 2Южно-Уральский государственный университет (национальный исследовательский университет), Челябинск, Россия 3Национальный исследовательский технологический университет «МИСиС», Москва, Россия
4 Балтийский федеральный университет им. И. Канта, Челябинск, Россия
5 Университет науки и технологий Пекина, Пекин, Китай а1зу@сзи.ти
Проведено исследование магнитных и магнитокалорических свойств поликристаллического Gd1oo_xErxAl2 (х = 0; 50). Установлено, что замена Gd на Ег существенно не влияет на величину изменения изотермической магнитной энтропии, которая равна Д^м = -5.0 Дж/(кгхК) при Тс = 163 К для GdAl2 и ДБм = -4.9 Дж/(кгхК) при Тс = 97 К для Gd0.5Er0.5Al2 (при изменении магнитного поля 3 Тл). Однако в сплаве Gd0.5Er0.5Al2 наблюдается большой магнитокалорический эффект в широком диапазоне температур ДТ = 66 К, что делает эти материалы перспективными для технологии магнитного охлаждения при низких температурах.
Ключевые слова: магнитокалорический эффект, магнитное охлаждение, фаза Лавеса, сжижение природного газа, ферромагнетик, редкоземельный элемент.
Поступила в редакцию 12.09.2020. После переработки 04.11.2020.
Сведения об авторах
Таскаев Сергей Валерьевич, доктор физико-математических наук, профессор кафедры физики конденсированного состояния, Челябинский государственный университет, Челябинск, Россия; научный сотрудник управления инновационной деятельности, ЮжноУральский государственный университет (национальный исследовательский университет), Челябинск, Россия; e-mail: tsv@csu.ru.
Ховайло Владимир Васильевич, доктор физико-математических наук, профессор, Национальный исследовательский технологический университет «Московский институт стали и сплавов», Москва, Россия, khovaylo@gmail.com.
Ульянов Максим Николаевич, кандидат физико-математических наук, старший научный сотрудник кафедры общей и прикладной физики, Челябинский государственный университет, Челябинск, Россия; научный сотрудник лаборатории исследования магнитных явлений на рентгеновских источниках нового поколения МНИЦ «Когерентная рентгеновская оптика для установок "Мегасайенс"», Балтийский федеральный университет им. И. Канта, Калининград, Россия; e-mail: max-39@yandex.ru.
Работа поддержана грантом РНФ № 18-42-06201.
Батаев Дмитрий Сергеевич, научный сотрудник, Челябинский государственный университет, Челябинск, Россия; e-mail: dimabataev@bk.ru.
Башарова Анастасия Андреевна, аспирант, Челябинский государственный университет, Челябинск, Россия; e-mail: velik0208@gmail.com.
Кононова Марина Валерьевна, аспирант, Челябинский государственный университет, Челябинск, Россия; Национальный исследовательский технологический университет «Московский институт стали и сплавов», Москва, Россия; e-mail: shchichko.marina.csu@gmail.com.
Плахотский Даниил Витальевич, аспирант, Челябинский государственный университет, Челябинск, Россия; e-mail: dp@csu.ru.
Богуш Михаил Юрьевич, аспирант, Челябинский государственный университет, Челябинск, Россия; e-mail: bmy74@yandex.ru.
Гаврилова Мария Алексеевна, студентка физического факультета, Челябинский государственный университет, Челябинск, Россия; e-mail: mariya-fks@mail.ru. Жеребцов Дмитрий Анатольевич, доктор химических наук, доцент, старший научный сотрудник управления инновационной деятельности, Южно-Уральский государственный университет (национальный исследовательский университет), Челябинск, Россия; e-mail: zherebtcovda@susu.ru.
Джанг Ху, профессор школы материаловедения и инженерии, Университет науки и технологий Пекина, Пекин, Китай; e-mail: zhanghu@ustb.edu.cn.
