Direct Measurement of the “Giant” Adiabatic Temperature Change in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Gd</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Si</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Ge</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mat

Giguère, Alexandre; Földeáki, M.; Gopal, B. R.; Chahine, Richard; Bose, T. K.; Frydman, A.; Barclay, J. A.

doi:10.1103/physrevlett.83.2262

Cited by 276 publications

(180 citation statements)

References 10 publications

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“…Actually, direct measurements of the temperature change in giant MCE compounds are scarce, and the reported values in many cases do not seem to be consistent with those indirectly computed. [14][15][16] Here, we report on adiabatic temperature measurements, which provide direct evidence of cooling by adiabatic magnetization in an inverse magnetocaloric material. It is also shown that heating is achieved at the paramagnetic-ferromagnetic phase transition.…”

Section: Introductionmentioning

confidence: 99%

Cooling and heating by adiabatic magnetization in theNi50Mn34In16magnetic shape-memory alloy

et al. 2007

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We report on measurements of the adiabatic temperature change in the inverse magnetocaloric Ni 50 Mn 34 In 16 alloy. It is shown that this alloy heats up with the application of a magnetic field around the Curie point due to the conventional magnetocaloric effect. In contrast, the inverse magnetocaloric effect associated with the martensitic transition results in the unusual decrease of temperature by adiabatic magnetization. We also provide magnetization and specific heat data which enable to compare the measured temperature changes to the values indirectly computed from thermodynamic relationships. Good agreement is obtained for the conventional effect at the second-order paramagnetic-ferromagnetic phase transition. However, at the first-order structural transition the measured values at high fields are lower than the computed ones. Irreversible thermodynamics arguments are given to show that such a discrepancy is due to the irreversibility of the first-order martensitic transition.

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Section: Introductionmentioning

confidence: 99%

Cooling and heating by adiabatic magnetization in theNi50Mn34In16magnetic shape-memory alloy

et al. 2007

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“…8,9 This paper is aimed at studying the entropy change ⌬S associated with the first-order magnetoelastic phase transition in Gd 5 (Si x Ge 1Ϫx ) 4 alloys, which has lately aroused much discussion. 5,[10][11][12][13] Two compositional ranges are of interest. For 0.24рxр0.5, the giant MCE is related to a firstorder magnetoelastic phase transition from a hightemperature paramagnetic ͑PM͒, monoclinic phase ( P112 1 /a) to a low-temperature ferromagnetic ͑FM͒, Gd 5 Si 4 -type orthorombic-I phase ( Pnma), at temperatures ranging from 130 K (xϭ0.24) to 276 K (xϭ0.5).…”

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confidence: 99%

“…We also unambiguously show that calorimetric values of ⌬S are in agreement with the indirect calculation obtained from the magnetization curves M (H), using the ClausiusClapeyron equation. 10,24 Gd 5 (Si x Ge 1Ϫx ) 4 alloys with xϭ0.1, 0.18, 0.2, 0.25, 0.3, 0.365, and 0.45 were prepared by arc melting admixtures of the pure elements in the desired stoichiometry under an argon atmosphere. As-cast buttons were cut into slices, and some were thermally treated for four hours at 950°C under a 10 Ϫ5 -torr vacuum.…”

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confidence: 99%

Scaling of the entropy change at the magnetoelastic transition inGd5(SixGe

et al. 2002

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Differential scanning calorimetry under a magnetic field H has been used to measure the entropy change ⌬S at the magnetoelastic transition in Gd 5 (Si x Ge 1Ϫx ) 4 alloys, for xр0.5. We show that ⌬S scales with the transition temperature, T t , which is tuned by x and H, from 70 to 310 K. Such a scaling demonstrates that T t is the relevant parameter in determining the giant magnetocaloric effect in these alloys, and proves that the magnetovolume effects due to H are of the same nature as the volume effects caused by substitution. DOI: 10.1103/PhysRevB.66.212402 PACS number͑s͒: 75.30.Sg, 75.20.En, 75.40.Cx, 75.50.Cc The magnetocaloric effect ͑MCE͒ has been studied for decades owing to its potential application to magnetic refrigerants. 1 The MCE is the isothermal entropy change or the adiabatic temperature change arising from the application or removal of a magnetic field H on a system with magnetic degrees of freedom. Many efforts have been devoted to the analysis of the MCE both in the vicinity of second-order magnetic phase transitions, where Gd is the element that shows the largest effect close to room temperature, 1,2 and in order-disorder blocking processes, e.g., in molecular magnets. 3 However, the MCE may be maximized in the vicinity of a first-order magnetoelastic phase transition, when the crystallographic transformation is field induced, resulting in an additional contribution to the entropy change 4,1 : a giant MCE has been discovered in the Gd 5 (Si x Ge 1Ϫx ) 4 compounds with xр0.5, [5][6][7] and recently in MnAs-based materials. 8,9 This paper is aimed at studying the entropy change ⌬S associated with the first-order magnetoelastic phase transition in Gd 5 (Si x Ge 1Ϫx ) 4 alloys, which has lately aroused much discussion. 5,10-13 Two compositional ranges are of interest. For 0.24рxр0.5, the giant MCE is related to a firstorder magnetoelastic phase transition from a hightemperature paramagnetic ͑PM͒, monoclinic phase ( P112 1 /a) to a low-temperature ferromagnetic ͑FM͒, Gd 5 Si 4 -type orthorombic-I phase ( Pnma), at temperatures ranging from 130 K (xϭ0.24) to 276 K (xϭ0.5). 6,14 The structural transition occurs by a shear mechanism 15 and yields a large volume contraction. The field-induced, reversible nature of the magnetostructural transition then results in strong magnetostriction 14 and giant ͑negative͒ magnetoresistance. 16 For xр0.2, a second-order PM-toantiferromagnetic ͑AFM͒ transition occurs at T N ͑from ϳ125 K for xϭ0 to ϳ135 K for xϭ0.2). 6 Upon further cooling, a first-order AFM-FM transition takes place, whose temperature ranges linearly from about 20 K (xϭ0) to 120 K (xϭ0.2). MCE is related to such a first-order phase transition. The nature of the AFM phase is currently under discussion, 17 and the magnetic structure may correspond to that of either a canted ferrimagnet, as proposed for Nd 5 Ge 4 ͑Ref. 18͒ or a canted antiferromagnet, as for the Ge-rich region of the Tb 5 (Si x Ge 1Ϫx ) 4 alloys. 19,20 The AFM-FM transition occurs simultaneously with a first-order structural tra...

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“…Previously, it has been shown both experimentally and theoretically that in compounds with first-order transitions displaying considerable hysteresis, the determination of DS M using the Maxwell relation is not reliable [14,15].…”

Section: Resultsmentioning

confidence: 99%

Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe11.6Si1.4

et al. 2016

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LaFe 11.6 Si 1.4 alloy has been synthesized in polycrystalline form using both arc melting and spark plasma sintering (SPS). The phase formation, hysteresis loss and magnetocaloric properties of the LaFe 11.6 Si 1.4 alloys synthesized using the two different techniques are compared. The annealing time required to obtain the 1:13 phase is significantly reduced from 14 days (using the arc melting technique) to 30 min (using the SPS technique). The magnetic entropy change (DS M ) for the arc-melted LaFe 11.6 Si 1.4 compound, obtained for a field change of 5 -0T (decreasing field), was estimated to be 19.6 J kg -1 K -1 . The effective RCP at 5T of the arc-melted LaFe 11.6 Si 1.4 compound was determined to be 360 J kg -1 which corresponds to about 88 % of that observed in Gd. A significant reduction in the hysteretic losses in the SPS LaFe 11.6 Si 1.4 compound was observed. The DS M , obtained for a field change of 5 -0T (decreasing field), for the SPS LaFe 11.6 Si 1.4 compound decreases to 7.4 J kg -1 K -1 . The T C also shifts from 186 (arc-melted) to 230 K (SPS) and shifts the order of phase transition from first to second order, respectively. The MCE of the SPS LaFe 11.6 Si 1.4 compound spreads over a larger temperature range with the RCP value at 5T reaching 288 J kg -1 corresponding to about 70 % of that observed in Gd. At low fields, the effective RCP values of the arc-melted and spark plasma-sintered LaFe 11.6 Si 1.4 compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe 11.6 Si 1.4 compounds in low-field magnetic refrigeration applications.

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Direct Measurement of the “Giant” Adiabatic Temperature Change inGd5Si2Ge2

Cited by 276 publications

References 10 publications

Cooling and heating by adiabatic magnetization in theNi50Mn34In16magnetic shape-memory alloy

Cooling and heating by adiabatic magnetization in theNi50Mn34In16magnetic shape-memory alloy

Scaling of the entropy change at the magnetoelastic transition inGd5(SixGe

Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe11.6Si1.4

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