Entropy change and magnetocaloric effect in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Gd</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ge</mml:mi></mml:mrow><mml:mrow><

Casanova, Fèlix; Batlle, X.; Labarta, A.; Marcos, Jordi; Mañosa, Lluís; Planes, Antoni

doi:10.1103/physrevb.66.100401

Cited by 104 publications

(91 citation statements)

References 13 publications

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“…As expected for magnetostructural transitions, 22 this value is larger than the transition entropy change 13 since it also includes the effect of magnetization changes with temperature beyond the transition region.…”

Section: ⌬S͑th͒mentioning

confidence: 92%

Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In

et al. 2007

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Applying a magnetic field to a ferromagnetic Ni 50 Mn 34 In 16 alloy in the martensitic state induces a structural phase transition to the austenitic state. This is accompanied by a strain which recovers on removing the magnetic field, giving the system a magnetically superelastic character. A further property of this alloy is that it also shows the inverse magnetocaloric effect. The magnetic superelasticity and the inverse magnetocaloric effect in Ni-Mn-In and their association with the first-order structural transition are studied by magnetization, strain, and neutron-diffraction studies under magnetic field.

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Section: ⌬S͑th͒mentioning

confidence: 92%

Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In

et al. 2007

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“…1 One of the most interesting features is the field-induced metamagnetic transition between AFM and FM states, which is coupled to a structural change 2 that gives the first-order nature of the transition. This magnetostructural transition yields a large variety of magnetoresponsive phenomena, such as giant magnetocaloric effect, 2-4,19 giant magnetoresistance, 5 large magnetostriction, 6,20 acoustic emission 21 or avalanche processes. 22,23 Although the equilibrium thermodynamic ground state at low temperatures is FM, 8 as in Si-doped compounds, 9 the AFM state is maintained when cooling down in the absence of an applied magnetic field, due to a kinetic arrest 8 that can be overcome by the application of magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Griffiths-like phase and magnetic correlations at high fields in Gd5Ge4

et al. 2011

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Magnetic correlations appearing in polycrystalline Gd 5 Ge 4 are studied. On the one hand, ac susceptibility measurements as functions of temperature at several dc fields and frequencies show the existence of ferromagnetic (FM) and antiferromagnetic (AFM) correlations in the paramagnetic (PM) region, where a Griffiths-like phase appears below ∼225 K. The value for the effective magnetic moment within the Griffiths-like phase is 10.1 μ B . FM correlations also extended all the way into the AFM phase below ∼127 K. The onset of the Griffiths-like phase is associated with an effective critical slowing down. On the other hand, high field magnetization measurements reveal the presence of FM and AFM correlations in the three magnetic phases (PM, FM, and AFM), giving rise to a variety of mixed magnetic states. In particular, at high fields the magnetostructural transition takes place in several stages that extend along a wide temperature range. A three-dimensional (T ,H,M) phase diagram is proposed, including the new experimental findings.

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“…26 Calorimetric curves shown in Fig. 1 were obtained after ZFC the sample from a temperature well above 130 K ͑which corresponds to the Néel temperature of the material͒ down to a given temperature T. This procedure was carried out at temperatures T = 4, 6,8,10,12,14,16,18,20,25,30,35,40, and 45 K. Calorimetric curves for 4-16 K are displayed in Fig. 1͑a͒.…”

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“…In the fully reversible regime, above 25 K, the major contribution to Q inc and Q dec comes from the latent heat associated with the first-order nature of the magnetostructural transition. 30,31 The difference ͉Q inc ͉ − ͉Q dec ͉ = Q diss thus represents the heat that the sample releases irreversibly in a close magnetic field cycle. Figure 2 shows that Q diss is almost temperature independent in the fully reversible regime and coincides with Q M , which indicates that Q diss is majorly due to the rearrangement of the magnetic domains.…”

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“…M͑T͒ curve on heating at 5 kOe after ZFC from 300 K showed a cuspid between 12 and 27 K, and the expected AFM-to-paramagnetic transition at Ӎ130 K, in agreement with previously reported results. 15,17 A second ZFC curve, recorded on heating at 5 kOe after applying a field of 50 kOe during a few seconds at 4 K, shows a strong decrease at ϳ25 K and matches the first ZFC curve above ϳ30 K. Isothermal magnetization curves were measured while increasing and decreasing the field after ZFC from above 130 K, at temperatures T = 4, 6,8,10,12,14,16,18,20,25,30,35,40, and 45 K. From 4 to 20 K, the magnetization curves while increasing the field showed the expected irreversible transition between AFM and FM phases, 15,17 the sample remaining in the FM phase after the field was further reduced down to zero. The presence of a 22% FM component in the virgin sample 16,22 was estimated from the saturation in the magnetization curve at 4 K, observed before the irreversible transition takes place.…”

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Giant heat dissipation at the low-temperature reversible-irreversible transition inGd5Ge4

2005

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The heat exchanged at the low-temperature first-order magnetostructural transition is directly measured in Gd 5 Ge 4 . Results show that the origin and the temperature dependence of the heat exchanged varies with the reversible/irreversible character of the first-order transition. In the reversible regime, the heat exchanged by the sample is mostly due to the latent heat at the transition and decreases with decreasing temperature, while in the irreversible regime, the heat is irreversibly dissipated and increases strongly with decreasing temperature, reaching a value of 237 J / kg at 4 K. 12 In order to enhance MCE at low temperatures, materials with a second-order phase transition have been investigated, such as ErAl 2 ͑Ref. 13͒ and ErNi 2 , 14 but as far as we know, MCE associated with a first-order phase transition below 20 K has not been reported.Gd 5 ͑Si x Ge 1−x ͒ 4 alloys have been extensively studied since the discovery of giant MCE in x ഛ 0.5 compounds. 3 Ge-rich compounds ͑x ഛ 0.2͒ present a first-order structural transition ranging from ϳ20 K ͑x =0͒ to ϳ120 K ͑x = 0.2͒, accompanied by a change in the magnetic ordering between antiferromagnetic ͑AFM͒ and ferromagnetic ͑FM͒ state, 3-5 which gives rise to a large entropy change. In particular, the unusual magnetic behavior shown by the end-compound Gd 5 Ge 4 at low temperatures has lately attracted a lot of interest. [15][16][17][18][19][20][21][22][23][24] In this alloy, the nature of the AFM ordering related to the high-temperature phase is complex, with competing AFM ͑between layers͒ and FM interactions ͑within layers͒. 5,[15][16][17][18] Moreover, due to this anisotropy in the exchange interactions, the magnetic ordering remains AFM without undergoing the structural transition after zero-field-cooling ͑ZFC͒ down to ϳ2 K. 15,19 The application of a certain magnetic field, whose value depends on the temperature, induces the first-order AFM-to-FM transition, which is irreversible at temperatures below ϳ10 K, partially reversible from ϳ10 to ϳ20 K and fully reversible above ϳ20 K ͑Refs. 15, 17, 20, and 21͒ as in the rest of Ge-rich compounds. The irreversibility of the transition might be due to a hindrance of the kinetics of the reversed AFM-FM transition, which at sufficiently low temperatures and high fields becomes arrested ͑i.e., structural relaxation time is larger than experimental time scales͒. 21,24 In this work, a study of the heat absorbed or released at the low-temperature irreversible and reversible first-order field-induced phase transitions is carried out in Gd 5 Ge 4 . Results show that the origin and the temperature dependence of the exchanged heat varies with the reversible/irreversible character of the first-order transition. In detail, the heat exchanged by the sample in the reversible regime is majorly due to the latent heat at the magnetostructural transition, while the heat dissipation associated with the magnetic work is much smaller. In contrast, in the irreversible regime, giant heat dissipation much larger than the latent heat...

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Entropy change and magnetocaloric effect inGd5(SixGe<

Cited by 104 publications

References 13 publications

Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In

Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In

Griffiths-like phase and magnetic correlations at high fields in Gd5Ge4

Giant heat dissipation at the low-temperature reversible-irreversible transition inGd5Ge4

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