Magnetocaloric effect in high-energy ball-milled Gd5Si2Ge2 and Gd5Si2Ge2/Fe nanopowders

Rajkumar, D.; Raja, M. Manivel; Gopalan, R.; Chandrasekaran, V.

doi:10.1016/j.jmmm.2007.12.005

Cited by 25 publications

(16 citation statements)

References 12 publications

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“…The effect of ball milling on the crystal structure, magnetization, and MCE of Gd 5 Si 2 Ge 2 and Gd 5 Si 2 Ge 1.9 Fe 0.1 alloys, and on the Gd 5 Si 2 Ge 2 /0.1 wt.% Fe mixture was studied by Rajkumar et al (2008). Both magnetization and MCE decrease with milling time.…”

Section: Miscellaneousmentioning

confidence: 99%

R5T4 Compounds

Mudryk

Pecharsky

Gschneidner

2014

Including Actinides

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Section: Miscellaneousmentioning

confidence: 99%

R5T4 Compounds

Mudryk

Pecharsky

Gschneidner

2014

Including Actinides

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“…Since the discovery of the giant magnetocaloric effect (GMCE) of the Gd 5 Si 2 Ge 2 alloy , a strong effort has been made in both materials and refrigeration device research to harness their superior performance. This has led to the use of various manufacturing techniques to achieve large‐scale manufacturing of GMCE materials, particularly melt‐spinning and powder metallurgy of La–Fe–Si‐based alloys, ball‐milling of Mn–Fe–P–As‐ and Gd–Si–Ge‐based alloys and tape casting of La–Ca–Sr–Mn‐based oxides . Nevertheless, a degree of chemical/structural disorder is expected in any real magnetic refrigerant material, and more so on those synthesized via large‐scale manufacturing starting from industrial‐grade precursors.…”

Section: Introductionmentioning

confidence: 99%

Disorder effects in giant magnetocaloric materials

Amaral

2014

Physica Status Solidi (a)

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In striving for mass production of magnetocaloric materials for refrigeration applications, one has to face the fact that these will not be laboratory‐grade materials, and will necessarily present (at the very least) composition gradients due to lower quality precursors. One can expect some probable consequences from this, namely that the maximum value of magnetic entropy change (ΔSM) will decrease compared to a pure material, but also some broadening of the ΔSM(T) curves should occur, as observed in some elementary ferromagnets. Some theoretical work has focused on this topic, for second‐order phase transition systems via the Landau theory of phase transitions and the molecular mean‐field model. Still, these theoretical considerations do not directly apply to first‐order phase transition (giant magnetocaloric effect) systems. We here present a study on the effect of disorder on the magnetic and magnetocaloric properties of first‐order phase transition systems. We employ the Bean–Rodbell model, and consider disorder to be described by a width of a Curie temperature distribution. We show how disorder effects “smooth” the discontinuities of magnetization and entropy change, and also affect magnetic hysteresis. We show how for sufficiently large disorder, the shape of the magnetic entropy curves approximate the distribution function. We discuss how the magnetic field dependence of magnetic entropy change is affected by disorder, in light of recent reports of “second‐order like” dependence of magnetic entropy change on applied magnetic field, for disordered giant magnetocaloric effect La–Fe–Si‐based samples.

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“…Among RE-based materials Gd 5 Si 2 Ge 2 , [13,14] La(FeSi) 13 , [15][16][17][18] RE 2 Fe 17 intermetallics, [19,20] clathrates Eu 8 Ga 16 Ge 30 , [21] and amorphous alloys [13,14,22] can be found. Among TM-based systems Heusler alloys, [23][24][25] MnAs, [26][27][28][29] cFeNi, [30][31][32] and amorphous alloys [33][34][35][36][37] can be found.…”

Section: Results On Mce Of Ball-milled Samplesmentioning

confidence: 99%

“…[57] Theoretical calculations were performed to explain the different behavior observed between rapid quenching and mechanically alloyed Co 62 Nb 6 Zr 2 B 30 amorphous samples. In order to do so, expression [14] was simplified to a summatory of discrete DS M (T,T C ) responses weighed using a Gaussian distribution of T C to describe the mechanically alloyed sample: [43] DS total M ðTÞ ¼ C…”

Section: Curie Temperature Distributionsmentioning

confidence: 99%

Analysis of the Magnetocaloric Effect in Powder Samples Obtained by Ball Milling

Blázquez

Ipus

Moreno-Ramírez

et al. 2015

Metallurgical and Materials Transactions E

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Since the discovery of the giant magnetocaloric effect (MCE) close to room temperature in FeRh and particularly in Gd 5 Si 2 Ge 2 compounds, the study of this phenomenon has experienced an exponential growth. Among the different techniques used to produce magnetocaloric materials, ball milling has been shown as a very versatile one and presents several advantages over other preparation techniques (e.g., easy scale-up to industrial production). Although a general decrease of the peak value of the magnetic entropy change is observed for milled samples, it can be compensated by the large broadening of the MCE peak, leading to an increase of the refrigeration capacity. In this short review, several aspects inherent to powder samples affecting MCE will be discussed, such as the relevant effect of the demagnetizing field, the possible multiphase character, and the presence of Curie temperature distributions. In mechanically alloyed samples, the two latter factors are typically affected by the degree of integration of the different starting constituents.

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Magnetocaloric effect in high-energy ball-milled Gd5Si2Ge2 and Gd5Si2Ge2/Fe nanopowders

Cited by 25 publications

References 12 publications

R5T4 Compounds

R5T4 Compounds

Disorder effects in giant magnetocaloric materials

Analysis of the Magnetocaloric Effect in Powder Samples Obtained by Ball Milling

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