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Zhao-hua Cheng - One of the best experts on this subject based on the ideXlab platform.
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giant magnetic Entropy Change in gadolinium orthoferrite near liquid hydrogen temperature
Journal of Alloys and Compounds, 2018Co-Authors: Xiangqun Zhang, Jiafu Wang, Zhao-hua ChengAbstract:Abstract The magnetic properties and giant magnetic Entropy Change in gadolinium orthoferrite have been investigated for their potential application as magnetic refrigeration working media. We found GdFeO3 polycrystalline sample exhibits a large magnetic Entropy Change value (–ΔSM = 50.2 J/kg K at 70 kOe) near the liquid hydrogen temperature, which is much larger than those of other oxide magnetic refrigerators. The large magnetocaloric effect is related to the half-filled 4f electronic state in rare earth-transition oxides. The large values of these parameters, together with negligible hysteresis, suggest that GdFeO3 multiferroic ferrite could be potential materials for magnetic refrigeration in low-temperature region.
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rotating field Entropy Change in hexagonal tmmno3 single crystal with anisotropic paramagnetic response
Physical Review B, 2012Co-Authors: Jinling Jin, Xiangqun Zhang, Zhao-hua ChengAbstract:The anisotropy of magnetic field- induced Entropy Change, -Delta S, was investigated in a hexagonal TmMnO3 single crystal at a temperature range of 2-50 K. The value of -Delta S along the c axis reaches a maximum of 8.73 J/kg K at 17 K in a field of 70 kOe, which is 20 times larger than that along the a axis. Our finding suggests that the rotating field Entropy Change -Delta S-R(alpha) from the a to c axis is attributed not only to magnetocrystalline anisotropy, but to thermal fluctuations.
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Low-field-induced magnetic Entropy Change in single-crystal Nd0.47Sr0.53MnO3
Journal of Physics: Condensed Matter, 2004Co-Authors: Guangjun Wang, Zhao-hua ChengAbstract:In this work, the discovery of a large low-field-induced magnetic Entropy Change in single-crystal Nd0.47Sr0.53MnO3 with A-type layered antiferromagnetic structure is reported. The magnetic Entropy Changes reach values of 11.0 and 11.5?J?kg?1?K?1 for field Changes of 20?kOe along the ab-plane andc-axis, respectively. The large magnetic Entropy Change occurring near TN was attributed to a low-field-induced antiferromagnetic ferromagnetic phase transition. Our results provide a possibility for development of magnetic refrigerant substances that are operable with a permanent magnet rather than a superconducting one as the magnetic field source.
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very large magnetic Entropy Change near room temperature in lafe11 2co0 7si1 1
Applied Physics Letters, 2002Co-Authors: Bao-gen Shen, Jirong Sun, Guangjun Wang, Zhao-hua ChengAbstract:A very large magnetic Entropy Change ΔS has been observed in Fe-based cubic NaZn13-type compound LaFe11.2Co0.7Si1.1 near the Curie temperature TC of 274 K. The value of the Entropy Change is ∼20.3 J/kg K under a magnetic field of 5 T at TC=274 K. It markedly exceeds that of pure Gd at the corresponding temperature range [V. K. Pecharsky & K. A. Gschneidner, Jr., Phys. Rev. Lett. 78, 4494 (1999)]. The great Entropy Change produced by the sharp Change of magnetization is associated with a large negative lattice expansion at TC. The very large magnetic Entropy Change and low cost suggest that the compound LaFe11.2Co0.7Si1.1 has great potential for applications as magnetic refrigerants near room temperature.
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Magnetic Entropy Change and magnetoresistance in the LaFe11.375Al1.625 compound
Journal of Applied Physics, 2002Co-Authors: Guangjun Wang, Jirong Sun, Zhao-hua Cheng, Xixiang Zhang, Jing Wang, Zhi-gang Sun, Cheng Dong, Hong Chen, Bao-gen ShenAbstract:Large magnetic Entropy Change |ΔS| with a nearly temperature-independent magnitude over a wide temperature range (about 70 K span from ∼140 K to 210 K) was observed in an Fe-based NaZn13-type compound LaFe11.375Al1.625. Such a behavior of magnetic Entropy Change is ascribed to two closely spaced magnetic transitions. One at 181 K (TN) with second-order nature is from the paramagnetic to antiferromagnetic state; another at 140 K (TO) with first-order nature, temperature hysteresis ∼5 K, is from antiferromagnetic to ferromagnetic state. At the antiferromagnetic to ferromagnetic transition a large Change of resistance was found, which can be induced as a function of temperature as well as field. The magnetoresistence under a field of 1 T reaches 3.4%.
Mohamed Oumezzine - One of the best experts on this subject based on the ideXlab platform.
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Large magnetic Entropy Change above 300 K in (La0.56Ce0.14)Sr0.3MnO3 perovskite
Journal of Alloys and Compounds, 2010Co-Authors: Sami Kallel, Nabil Kallel, Octavio Peña, Ahmed Hagaza, Mohamed OumezzineAbstract:Magnetic field dependence of the magnetic Entropy Change (ΔSM) is the key for magnetic refrigeration. A large magnetic Entropy Change (ΔSM) associated with the ferromagnetic-paramagnetic transition in Ce-doped La0.7Sr0.3MnO3 material has been observed. It is shown for (La0.56Ce0.14)Sr0.3MnO3 composition at the Curie temperature of 357 K, that the maxima of the magnetic Entropy Changes View the MathML sourceΔSMmax upon variation of the applied magnetic field at 1 and 5 T are about 1.55 and 4.78 J kg−1 K−1, respectively. Due to the large (ΔSM) and high Curie temperature, the (La0.56Ce0.14)Sr0.3MnO3 perovskite is suggested to be used as potential magnetic refrigerants for magnetic refrigeration technology above room temperature.
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Determination of the spontaneous magnetization by analysis of the magnetic Entropy Change in La0.40Nd0.30Sr0.30Mn0.70Cr0.30O3
Journal of Alloys and Compounds, 2010Co-Authors: Sami Kallel, Nabil Kallel, Octavio Peña, Mohamed OumezzineAbstract:The magnetic phase transition and magnetic Entropy Change (−ΔSM) in the La0.40Nd0.30Sr0.30Mn0.70Cr0.30O3 perovskite were investigated by measuring the magnetization as a function of temperature. The ferromagnetic transition temperature TC and the critical exponents β and γ, determined by analyzing the Arrott plots, are found to be TC = 191 K, β = 0.433, γ = 1.053 and δ = 3.486. These values for the critical exponents are close to the mean-field values. In order to estimate the spontaneous magnetization Ms(T) at a given temperature, we use a process based on the analysis, in the mean-field theory, of the magnetic Entropy Change (−ΔSM) versus the magnetization data. An excellent agreement is found between the spontaneous magnetization determined from the Entropy Change ((−ΔSM) vs. M2) and the classical extrapolation from the Arrott curves (μ0H/M vs. M2), thus confirming that the magnetic Entropy is a valid approach to estimate the spontaneous magnetization in this system and in other compounds as well.
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Large magnetic Entropy Change above 300K in (La0.56Ce0.14)Sr0.3MnO3 perovskite
Journal of Alloys and Compounds, 2010Co-Authors: Sami Kallel, Nabil Kallel, Octavio Peña, Ahmed Hagaza, Mohamed OumezzineAbstract:International audienceMagnetic field dependence of the magnetic Entropy Change (ΔSM) is the key for magnetic refrigeration. A large magnetic Entropy Change (ΔSM) associated with the ferromagnetic-paramagnetic transition in Ce-doped La0.7Sr0.3MnO3 material has been observed. It is shown for (La0.56Ce0.14)Sr0.3MnO3 composition at the Curie temperature of 357 K, that the maxima of the magnetic Entropy Changes View the MathML sourceΔSMmax upon variation of the applied magnetic field at 1 and 5 T are about 1.55 and 4.78 J kg−1 K−1, respectively. Due to the large (ΔSM) and high Curie temperature, the (La0.56Ce0.14)Sr0.3MnO3 perovskite is suggested to be used as potential magnetic refrigerants for magnetic refrigeration technology above room temperature
Sami Kallel - One of the best experts on this subject based on the ideXlab platform.
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Large magnetic Entropy Change above 300 K in (La0.56Ce0.14)Sr0.3MnO3 perovskite
Journal of Alloys and Compounds, 2010Co-Authors: Sami Kallel, Nabil Kallel, Octavio Peña, Ahmed Hagaza, Mohamed OumezzineAbstract:Magnetic field dependence of the magnetic Entropy Change (ΔSM) is the key for magnetic refrigeration. A large magnetic Entropy Change (ΔSM) associated with the ferromagnetic-paramagnetic transition in Ce-doped La0.7Sr0.3MnO3 material has been observed. It is shown for (La0.56Ce0.14)Sr0.3MnO3 composition at the Curie temperature of 357 K, that the maxima of the magnetic Entropy Changes View the MathML sourceΔSMmax upon variation of the applied magnetic field at 1 and 5 T are about 1.55 and 4.78 J kg−1 K−1, respectively. Due to the large (ΔSM) and high Curie temperature, the (La0.56Ce0.14)Sr0.3MnO3 perovskite is suggested to be used as potential magnetic refrigerants for magnetic refrigeration technology above room temperature.
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Determination of the spontaneous magnetization by analysis of the magnetic Entropy Change in La0.40Nd0.30Sr0.30Mn0.70Cr0.30O3
Journal of Alloys and Compounds, 2010Co-Authors: Sami Kallel, Nabil Kallel, Octavio Peña, Mohamed OumezzineAbstract:The magnetic phase transition and magnetic Entropy Change (−ΔSM) in the La0.40Nd0.30Sr0.30Mn0.70Cr0.30O3 perovskite were investigated by measuring the magnetization as a function of temperature. The ferromagnetic transition temperature TC and the critical exponents β and γ, determined by analyzing the Arrott plots, are found to be TC = 191 K, β = 0.433, γ = 1.053 and δ = 3.486. These values for the critical exponents are close to the mean-field values. In order to estimate the spontaneous magnetization Ms(T) at a given temperature, we use a process based on the analysis, in the mean-field theory, of the magnetic Entropy Change (−ΔSM) versus the magnetization data. An excellent agreement is found between the spontaneous magnetization determined from the Entropy Change ((−ΔSM) vs. M2) and the classical extrapolation from the Arrott curves (μ0H/M vs. M2), thus confirming that the magnetic Entropy is a valid approach to estimate the spontaneous magnetization in this system and in other compounds as well.
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Large magnetic Entropy Change above 300K in (La0.56Ce0.14)Sr0.3MnO3 perovskite
Journal of Alloys and Compounds, 2010Co-Authors: Sami Kallel, Nabil Kallel, Octavio Peña, Ahmed Hagaza, Mohamed OumezzineAbstract:International audienceMagnetic field dependence of the magnetic Entropy Change (ΔSM) is the key for magnetic refrigeration. A large magnetic Entropy Change (ΔSM) associated with the ferromagnetic-paramagnetic transition in Ce-doped La0.7Sr0.3MnO3 material has been observed. It is shown for (La0.56Ce0.14)Sr0.3MnO3 composition at the Curie temperature of 357 K, that the maxima of the magnetic Entropy Changes View the MathML sourceΔSMmax upon variation of the applied magnetic field at 1 and 5 T are about 1.55 and 4.78 J kg−1 K−1, respectively. Due to the large (ΔSM) and high Curie temperature, the (La0.56Ce0.14)Sr0.3MnO3 perovskite is suggested to be used as potential magnetic refrigerants for magnetic refrigeration technology above room temperature
Bao-gen Shen - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Entropy Change and refrigerant capacity in GdFeAl compound
Journal of Applied Physics, 2009Co-Authors: Qin Dong, Bao-gen Shen, Junxiu Chen, Jie Shen, Haiwu Zhang, Jirong SunAbstract:Magnetic properties and magnetocaloric effect of GdFeAl compound have been investigated. The small saturated magnetization of GdFeAl compound is caused by the antiferromagnetic coupling between the magnetic moments of Gd and Fe atoms. A second-order magnetic phase transition is confirmed around 265K. The maximum magnetic Entropy Change for GdFeAl compound is 3.7Jkg−1K−1 under the field Change of 0–5T. However, a large refrigerant capacity of 420Jkg−1 is obtained, which is due to the large full width at half peak of the magnetic Entropy Change versus temperature curve in GdFeAl compound.
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Field-induced Entropy Change in the manganite with significant short-range magnetic order
Applied Physics Letters, 2006Co-Authors: Lichao Jia, Jirong Sun, Haiwu Zhang, Guipeng Liu, J. Z. Wang, Bao-gen ShenAbstract:Effects of short-range magnetic order on magnetic Entropy Change have been studied for the manganese oxide Eu0.55Sr0.45MnO3. Superparamagnetic clusters composed of seven to ten Mn ions, depending on applied field, have been derived in the paramagnetic state of the compound based on the analysis of dc susceptibility. The presence of short-range magnetic order greatly depresses the magnetic Entropy of the paramagnetic phase; thus the Entropy Changes at the field-induced paramagnetic to ferromagnetic phase transition. The maximum Entropy Change detected is only ∼7J∕kgK for a field Change of 0–5T, about one-fifth of the theoretical expectation. The experimental results can be well elucidated within the mean field theory. It is suggested that a way of destroying the short-range order would enhance the magnetic Entropy Change greatly.
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very large magnetic Entropy Change near room temperature in lafe11 2co0 7si1 1
Applied Physics Letters, 2002Co-Authors: Bao-gen Shen, Jirong Sun, Guangjun Wang, Zhao-hua ChengAbstract:A very large magnetic Entropy Change ΔS has been observed in Fe-based cubic NaZn13-type compound LaFe11.2Co0.7Si1.1 near the Curie temperature TC of 274 K. The value of the Entropy Change is ∼20.3 J/kg K under a magnetic field of 5 T at TC=274 K. It markedly exceeds that of pure Gd at the corresponding temperature range [V. K. Pecharsky & K. A. Gschneidner, Jr., Phys. Rev. Lett. 78, 4494 (1999)]. The great Entropy Change produced by the sharp Change of magnetization is associated with a large negative lattice expansion at TC. The very large magnetic Entropy Change and low cost suggest that the compound LaFe11.2Co0.7Si1.1 has great potential for applications as magnetic refrigerants near room temperature.
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Magnetic Entropy Change and magnetoresistance in the LaFe11.375Al1.625 compound
Journal of Applied Physics, 2002Co-Authors: Guangjun Wang, Jirong Sun, Zhao-hua Cheng, Xixiang Zhang, Jing Wang, Zhi-gang Sun, Cheng Dong, Hong Chen, Bao-gen ShenAbstract:Large magnetic Entropy Change |ΔS| with a nearly temperature-independent magnitude over a wide temperature range (about 70 K span from ∼140 K to 210 K) was observed in an Fe-based NaZn13-type compound LaFe11.375Al1.625. Such a behavior of magnetic Entropy Change is ascribed to two closely spaced magnetic transitions. One at 181 K (TN) with second-order nature is from the paramagnetic to antiferromagnetic state; another at 140 K (TO) with first-order nature, temperature hysteresis ∼5 K, is from antiferromagnetic to ferromagnetic state. At the antiferromagnetic to ferromagnetic transition a large Change of resistance was found, which can be induced as a function of temperature as well as field. The magnetoresistence under a field of 1 T reaches 3.4%.
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Magnetic Entropy Change in La(Fe0.98Co0.02)11.7Al1.3
Journal of Physics: Condensed Matter, 2000Co-Authors: Bao-gen Shen, Jirong Sun, Zhao-hua Cheng, Xixiang ZhangAbstract:Magnetization of compound La(Fe0.98Co0.02)11.7Al1.3 was measured carefully as functions of temperature and applied field around its Curie temperature of ~198 K. Magnetic Entropy Change |ΔS|, allowing estimation of the magnetocaloric effect (MCE), was determined based on thermodynamic Maxwell's relation. The achieved magnitude of |ΔS| reaches 10.6 J kg-1 K-1 under a field of 5 T. The considerable Entropy Change is believed to be due to the high magnetization and the sharp Change in magnetization at TC. It is found that the magnetic phase transition is completely reversible in temperature, indicating a nature of second-order phase transition.
Antoni Planes - One of the best experts on this subject based on the ideXlab platform.
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direct observation of the magnetic field induced Entropy Change in gd5 sixge1 x 4 giant magnetocaloric alloys
Applied Physics Letters, 2005Co-Authors: Felix Casanova, Lluís Mañosa, X Batlle, A Labarta, Francisco J Perezreche, Eduard Vives, Antoni PlanesAbstract:Direct observation of the Entropy Change in a first-order phase transition is obtained by using a differential scanning calorimeter in which the transition is field-induced under the application of an external magnetic field. This procedure enables direct evaluation of the magnetocaloric effect in materials showing first-order magnetostructural phase transitions. Results for Gd5(SixGe1−x)4 giant magnetocaloric alloys are reported. Calorimetric curves sweeping the field through the transition reveal a unusual increase of the Entropy Change with cycling. This increase is accounted for by considering both the structural and magnetic contributions to the total Entropy Change.
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magnetic field induced Entropy Change and magnetoelasticity in ni mn ga alloys
Physical Review B, 2002Co-Authors: Jordi Marcos, Lluís Mañosa, Antoni Planes, Felix Casanova, X Batlle, A Labarta, B MartinezAbstract:The magnetocaloric effect that originates from the martensitic transition in the ferromagnetic Ni-Mn-Ga shape-memory alloy is studied. We show that this effect is controlled by the magnetostructural coupling at both the martensitic variant and magnetic domain length scales. A large Entropy Change induced by moderate magnetic fields is obtained for alloys in which the magnetic moment of the two structural phases is not very different. We also show that this Entropy Change is not associated with the Entropy difference between the martensitic and the parent phase-arising from the Change in the crystallographic structure-which has been found to be independent of the magnetic field within this range of fields.
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Entropy Change and magnetocaloric effect in gd5 sixge1 x 4
Physical Review B, 2002Co-Authors: Felix Casanova, Lluís Mañosa, X Batlle, A Labarta, Jordi Marcos, Antoni PlanesAbstract:Isothermal magnetization curves up to 23 T have been measured in Gd 5 Si 1 . 8 Ge 2 . 2 . We show that the values of the Entropy Change at the first-order magnetostructural transition, obtained from the Clausius-Clapeyron equation and the Maxwell relation, are coincident, provided the Maxwell relation is evaluated only within the transition region and the maximum applied field is high enough to complete the transition. These values are also in agreement with the Entropy Change obtained from differential scanning calorimetry. We also show that a simple phenomenological model based on the temperature and field dependence of the magnetization accounts for these results.
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Entropy Change of martensitic transformations in Cu-based shape-memory alloys.
Physical review. B Condensed matter, 1993Co-Authors: Lluís Mañosa, Antoni Planes, Jordi Ortín, Benjamín MartínezAbstract:We have investigated the different contributions to the Entropy Change at the martensitic transition of different families of Cu-based shape-memory alloys. The total Entropy Change has been obtained through calorimetric measurements. By measuring the evolution of the magnetic susceptibility with temperature, the Entropy Change associated with conduction electrons has been evaluated. The contribution of the anharmonic vibrations of the lattice has also been estimated using various parameters associated with the anharmonic behavior of these alloys, collected from the literature. The results found in the present work have been compared to values published for the martensitic transition of group-IV metals. For Cu-based alloys, both electron and anharmonic contributions have been shown to be much smaller than the overall Entropy Change. This finding demonstrates that the harmonic vibrations of the lattice are the most relevant contribution to the stability of the bcc phase in Cu-based alloys.