Studies of magnetic properties for the Gd3Zr10Fe55Co10Mo5W2B15 glassy alloy are presented. The morphous
structure of melt-spun ribbon of investigated alloy was confirmed by X-ray diffractometry. The Curie temperature
TC was determined analyzing M(H) dependences measured at various temperatures as well as from M(T) dependence measured at low constant magnetic field. Furthermore, the isothermal magnetic entropy changes j   SMj were calculated from the magnetization curves to assess the possibility of potential application of studied samples as active elements in magnetic refrigerators

Chrobak, Anna

Kotynia, K.

Pawlik, P.

Acta Physica Polonica A

Repozytorium Uniwersytetu Śląskiego RE-BUŚ

             Title: Magnetic properties of the rapidly solidified Gd3Zr10Fe55Co10Mo5W2B15 alloy  Author: K. Kotynia, Anna Chrobak, P. Pawlik  Citation style: Kotynia K., Chrobak Anna, Pawlik P. (2019). Magnetic properties of the rapidly solidified Gd3Zr10Fe55Co10Mo5W2B15 alloy. "Acta Physica Polonica A" (Vol. 136, nr 5 (2019), s. 696-700), doi: 10.12693/APhysPolA.136.696  Vol. 136 (2019) ACTA PHYSICA POLONICA A No. 5Proc. of the 13th Symposium of Magnetic Measurements and Modeling SMMM’2018, Wieliczka, Poland, October 8–10, 2018Magnetic Properties of the Rapidly SolidifiedGd3Zr10Fe55Co10Mo5W2B15 AlloyK. Kotyniaa,∗, A. Chrobakb and P. PawlikaaInstitute of Physics, Częstochowa University of Technology, Al. Armii Krajowej 19, 42-200 Częstochowa, PolandbInstitute of Materials Science, University of Silesia, 75 Pułku Piechoty 1, 41-500 Chorzów, PolandStudies of magnetic properties for the Gd3Zr10Fe55Co10Mo5W2B15 glassy alloy are presented. The amorphousstructure of melt-spun ribbon of investigated alloy was confirmed by X-ray diffractometry. The Curie temperatureTC was determined analyzing M(H) dependences measured at various temperatures as well as from M(T ) depen-dence measured at low constant magnetic field. Furthermore, the isothermal magnetic entropy changes | −∆SM |were calculated from the magnetization curves to assess the possibility of potential application of studied samplesas active elements in magnetic refrigerators.DOI: 10.12693/APhysPolA.136.696PACS/topics: 78.55.Qr, 71.20.Eh, 75.50.Bb, 75.50.Kj1. IntroductionThe growing interest in magnetocaloric materials wascaused by using them in cooling systems operating nearroom temperature. Moreover, in recent years, the mag-netocaloric effect was also used in the power industry toconvert industrial waste heat to electricity [1]. There arethree physical quantities that designate the usefulness ofmagnetocaloric materials: the magnetic entropy change|−∆SM |, the adiabatic temperature change |−∆Tad|, andthe relative cooling power (RCP) [2]. An ideal magneticrefrigerant material should exhibit large values of both|−∆SM | and |−∆Tad|, as well as high RCP around roomtemperature at the low magnetic field [3]. High magneticentropy change was found in Gd5(Si2Ge2) [4], MnAs [5],and MnFe(P,As) alloys [6]. The first order magneto-structural phase transition and the appearance of hys-teretic losses were observed for these alloys. Althoughthese materials reveal significant | −∆SM | and | −∆Tad|their major drawbacks are low RCP and complex process-ing route. Despite relatively low | −∆SM | and | −∆Tad|values, due to second order magnetic phase transition,the amorphous alloys seems to be an interesting alterna-tive for their large RCP and low processing costs.Until now we have performed studies of the mag-netocaloric effect for GdxZr10Fe58−xCo10Mo5W2B15(where x = 0, 1, 2, 3, 4, 5 at.%), that have showngood glass forming abilities for all investigated composi-tions [7]. Furthermore, increase in Gd contents resultedin the increase of the Curie temperature of amorphousphase [8]. Besides, in all cases a broad | − ∆SM | peakaround TC was observed [8–10]. Therefore the aim of thepresent work was to investigate the influence of furtheradmixture of Gd on structural and magnetocaloric prop-erties of the Gd3Zr10Fe55Co10Mo5W2B15 alloy.∗corresponding author; e-mail: k.kotynia@po.edu.pl2. Sample preparationand experimental methodsThe Gd3Zr10Fe55Co10Mo5W2B15 alloy was obtainedby the arc-melting of the high purity (99.98%) con-stituent elements Gd, Zr, Fe, Co, Mo, W with the ad-dition of pre-alloyed Fe–B. Alloy composition representsnominal atomic percentage. To protect oxidation duringmelting the titanium was used as a getter. The ingotwas re-melted seven times to guarantee a homogeneityof the alloy.The ribbon was prepared by the melt-spinning tech-nique at a surface velocity of the copper roll of 32 m/s.Both the arc-melting and melt-spinning techniques wereperformed under an Ar atmosphere to avoid oxidation.The phase structure was investigated by the X-raydiffractometry (XRD) using the Bruker D8 Advancediffractometer with Cu Kα radiation and the LynxEyedetector. The data were recorded using the Bragg–Brentano continuous-scan method in 2Θp range between30 and 100 degrees.The field dependences of magnetization were recordedin the field cooling mode (FC) by SQUID MPMS XL-7Quantum Design system. The magnetic measurementsM(H) were performed in the temperature range between150 K and 350 K. Based on those results the Arrott plotswere constructed. Magnetocaloric effect MCE was esti-mated by calculation of the temperature dependences ofmagnetic entropy change | − ∆SM | for various changesof external magnetic fields according to the Maxwellthermodynamic formula [11]:∆SM (TH) =H∫0(∂M(T,H)∂T)HdH, (1)where T is temperature, M(T,H) is magnetization, H isexternal magnetic field.(696)Magnetic Properties of the Rapidly Solidified Gd3Zr10Fe55Co10Mo5W2B15 Alloy 6973. ResultsX-ray diffraction pattern measured for the melt-spun ribbon of the Gd3Zr10Fe55Co10Mo5W2B15 alloyis shown in Fig. 1.A broad peak between 2Θ = 30 deg and 50 degsuggests amorphous structure of the rapidly solidifiedribbon.One of the most important parameters which fa-cilitates the potential applicability of a material inthe magnetic refrigeration is the Curie temperature TC .In order to determine TC we have used four methods de-scribed below.Fig. 1. XRD pattern measured for melt-spun ribbon ofthe Gd3Zr10Fe55Co10Mo5W2B15 alloy.3.1. Determination of TC from dM/dT dependenceThe temperature dependence of magnetization wasshown in Fig. 2.The M(T ) curve is typical for the amorphous mate-rials. The magnetization gradually decreases with theincrease of temperature around TC. For this purposethe dM/dT derivative was calculated and TC reaching316 K was determined as a temperature correspondingto the minimum value of dM/dT .3.2. Determination of TC using critical exponentin Heisenberg modelIn amorphous alloys the change of magnetizationaround the Curie temperature proceeds gradually, unlikein the case of crystalline counterparts (where magnetiza-tion radically drops at TC). Therefore it is more difficultto designate precisely the TC in glassy samples. To solvethis problem for the same M(T ) dependence as shownin Fig. 2 one can use the relation [12]:M (T ) = Ms (0)(1− TTC)β, (2)Fig. 2. Temperature dependence of magnetizationM(T ) and its derivative dM/dT measured atµ0H = 0.01 T for the Gd3Zr10Fe55Co10Mo5W2B15 al-loy ribbon.Fig. 3. The temperature T dependence of normalizedmagnetization M/Mmax measured for the amorphousribbon sample of the Gd3Zr10Fe55Co10Mo5W2B15 alloy.Inset — the modified (M/Mmax)1/β vs. T curve, whereβ is the critical parameter (β = 0.365) for the Heisen-berg model.where M(T ) is magnetization at temperature T , MS(0)is saturation magnetization at T = 0 K, and β is criti-cal exponent which for the Heisenberg model is equal to0.365 [13]. The temperature T dependence of the normal-ized magnetization (M/Mmax)1/β calculated using theformula (2) and determination of TC = 316 K were shownin Fig. 3.3.3. Determination of the phase transitionand TC using Arrott plotsThe magnetization curves were measured at varioustemperatures between 150 K and 340 K in external mag-netic fields up to 7 T.698 K. Kotynia, A. Chrobak, P. PawlikFig. 4. Arrott plots, i.e. M2 versus µ0H/M forthe Gd3Zr10Fe55Co10Mo5W2B15 glassy alloy in as-caststate.Fig. 5. Spontaneous magnetization M2sp ofGd3Zr10Fe55Co10Mo5W2B15 alloy ribbon vs. tem-perature T .In order to determine the type of the mag-netic phase transition and confirm TC value obtainedfrom previous measurements, the Arrott plots wereconstructed (Fig. 4).The shapes of the Arrott plots are typical for alloysin which the second order phase transtion from ferro- toparamagnetic state around the Curie temperature takesplace.FromM2(µ0H/M) curves the relationM2sp versus tem-perature T was constructed and TC was determined. M2spvalues determined using extrapolations of the linear partsof M2 vs. µ0H/M curves. Each M2sp value was readas the interception of those extrapolations with M2 axis(presented in Fig. 5).The TC calculated in this way reaches 315 K, whichis in good agreement with the values obtained using twopreviously described methods.3.4. Determination of TC using µ0H(T ) diagramAnother approach to verify TC value was presentedin Figs. 6–8. The magnetization isothermsM(µ0H) werecut across by constant magnetizations Mi = M1, M2,M3, M4, M5, and M6 (Fig. 6).Fig. 6. The magnetic field µ0H dependences of magne-tization M measured at various temperatures from 154to 340 K (∆T = 6 K) for the amorphous ribbon of theGd3Zr10Fe55Co10Mo5W2B15 alloy.Fig. 7. µ0H(T ) plot for the amorphousGd3Zr10Fe55Co10Mo5W2B15 alloy ribbon.As a next step, the magnetic fields µ0Hi,j correspond-ing to the particular constant magnetizations Mi wereread from M(µ0H) curves measured at various temper-atures (from Fig. 6).The temperature dependences of µ0Hij correspondingto constant magnetizations Mi are presented in Fig. 7.Subsequently the linear parts of µ0H(T ) curveswere linearly extrapolated to the zero magnetic fieldsand corresponding Ti temperatures were determined.Finally, the relation Mi vs. Ti was constructed andpresented in Fig. 8.Magnetic Properties of the Rapidly Solidified Gd3Zr10Fe55Co10Mo5W2B15 Alloy 699Fig. 8. Mi versus Ti for the amorphousGd3Zr10Fe55Co10Mo5W2B15 alloy ribbon.Fig. 9. Temperature dependence of the magneticentropy changes | − ∆SM | for the amorphousGd3Zr10Fe55Co10Mo5W2B15 alloy ribbon.The Curie point was determined as an extrapolationof Mi(Ti) curve to M = 0. The TC value obtained usingthis method reached 312 K.This value is slightly lower than those obtained by pre-vious methods. However, it is more likely that twofoldextrapolation used in this approach gives rise to potentialsystematic error.3.5. Magnetocaloric effectIn order to assess the magnetocaloric effect in the in-vestigated alloy the magnetic entropy change | − ∆SM |vs. temperature T at various changes of magnetic fieldswere calculated using Eq. (1), based on measurementof M(H) curves presented in Fig. 6. The tempera-ture dependences of | − ∆SM | were shown in Fig. 9.In all cases |−∆SM | reaches maximum around the Curiepoint. The maximum value of | − ∆SmaxM | reached1.75 J/(kg K) for the change of external magnetic fieldup to µ0H = 7 T.Based on our previous studies of the amorphousGdxZr10Fe58−xCo10Mo5W2B15 (x = 0, 1) alloy rib-bons the increase of Gd contents to 3 at.% causedan increase of the Curie temperature without significantchange of | −∆SmaxM |.4. ConclusionThe XRD studies of the melt-spun ribbon samplesof the Gd3Zr10Fe55Co10Mo5W2B15 alloy have showntheir glassy structure. For this reason four differentmethods allowing to determine the Curie temperature,were used. All used methods have shown similar TC val-ues reaching 316 K. Relatively large TC in comparison tothe amorphous GdxZr10Fe58−xCo10Mo5W2B15 (x = 0,1) alloy ribbons can be related to a higher Gd contentin the studied sample. The tunable TC around roomtemperature makes these alloys potentially useful for de-velopment of magentocaloric regenerators. Furthermore,construction of the Arrott plots confirmed a presence ofsecond order phase transition around TC.Magnetic entropy change exhibits maximum atthe Curie point (≈ 315 K) and reaches 1.75 J/(kg K) forthe change of external magnetic field up to 7 T. Obtainedvalues of | −∆SM | peaks for various changes of externalmagnetic fields are comparable to those obtained for theGdxZr10Fe58−xCo10Mo5W2B15 (x = 0, 1 alloy ribbons.Furthermore, wide bump of |−∆SM | vs. T suggests thatthe RCP should be large for the investigated alloy andseems to be promising for application.References[1] D. Vuarnoz, A. Kitanovski, C. Gonin, Y. Borgeaud,M. Delessert, P.W. Meinen, M. Egolf, J. Appl. Eng.100, 229 (2012).[2] V. Chaudhary, D.V.D. Repaka, A. Chaturvedi,I. Sridhar, R.V. Ramanujan, J. Appl. Phys. 116,163918 (2014).[3] P. Shamba, R. Zeng, J.L. Wang, S.J. Campbell,S.X. Dou, J. Magn. Magn. Mater. 331, 102 (2013).[4] A.O. Pecharsky, K.A. Gschneidner, V.K. Pecharsky,J. Appl. Phys. 93, 4722 (2003).[5] H. Wada, T. Asano, J. Magn. Magn. Mater. 290,703 (2005).[6] H. Yibole, F. Guillou, L. Zhang, N.H.V. Dijk,E. Brück, J. Phys. D Appl. Phys. 47, 1 (2014).[7] K. Kotynia, P. Pawlik, M. Hasiak, Hutnik Wiado-mości Hutnicze 84, 425 (2017).[8] K. Kotynia, P. Pawlik, A. Chrobak, in: Works ofXLV School of Material Engineering, Kraków–Rytro(Poland), 2017, p. 106.700 K. Kotynia, A. Chrobak, P. Pawlik[9] K. Kotynia, P. Pawlik, M. Hasiak, M. Pruba,K. Pawlik, Acta Phys. Pol. A 131, 1204 (2017).[10] K. Kotynia, A. Chrobak, P. Pawlik, in: Works ofXLVI School of Material Engineering, Kraków–Rytro(Poland), 2018, p. 85.[11] K.A. Gschneidner, J.V.K. Pecharsky, Ann. Rev.Mater. Sci. 30, 387 (2000).[12] L. Banas, Z. Brzeźniak, M. Neklyudov, A. Prohl, in:Stochastic Ferromagnetism, Walter de Gruyter, 2014,p. 198.[13] F. Ben Jemaa, S.H. Mahmood, M. Ellouze, E.K. Hlil,F. Halouani, J. Mater. Sci. 49, 6883 (2014).

Magnetic properties of the rapidly solidified Gd3Zr10Fe55Co10Mo5W2B15 alloy

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Magnetic properties of the rapidly solidified Gd3Zr10Fe55Co10Mo5W2B15 alloy

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