Papers on magnetocaloric effect
Find below all of the papers published after January 2007 on the Magnetocaloric Effect and Its Applications. If you find some mistake, please, contact us.
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Title: Magnetocaloric effect of GdCo2-xAlx compounds
Author(s): Gu ZF (Gu, Zhengfei), Zhou B (Zhou, Bo), Li JQ (Li, Junqin), Ao WQ (Ao, Weiqin), Cheng G (Cheng, Gang), Zhao HC (Zhao, Hacheng)
Source: SOLID STATE COMMUNICATIONS 141 (10): 548-550 MAR 2007
Abstract: The structure, magnetic property and magnetocaloric effect of GdCo2-xAlx (x = 0, 0.06, 0.12, 0.18, 0.24, 0.4) compounds have been investigated by X-ray diffraction (XRD) and magnetic measurement techniques. The experimental results show that the GdCo2-xAlx (x >= 0.4) compounds are single phase with a Laves-phase MgCu2-type structure. The Curie temperature T-c initially increases, and then decreases with increasing Al content. The maximum value of T-c 418 K, is reached for the compound with x = 0.06. The magnetic entropy change, which is determined from the temperature and field dependence of the magnetization by the Maxwell relation, decreases almost linearly with increasing Al content. (C) 2007 Elsevier Ltd. All rights reserved.
Title: Crystallography, anisotropic metamagnetism, and magnetocaloric effect in Tb5Si2.2Ge1.8
Author(s): Zou M (Zou, M.), Mudryk Y (Mudryk, Ya.), Pecharsky VK (Pecharsky, V. K.), Gschneidner KA (Gschneidner, K. A., Jr.), Schlagel DL (Schlagel, D. L.), Lograsso TA (Lograsso, T. A.)
Source: PHYSICAL REVIEW B 75 (2): Art. No. 024418 JAN 2007
Abstract: The metamagnetic-like transitions and giant magnetocaloric effect were observed with the magnetic field applied parallel to the a and c axes, but not the b axis in a Tb5Si2.2Ge1.8 single crystal. The in situ x-ray powder diffraction study indicates that these metamagnetic-like transitions are coupled to crystallographic phase transformations occurring via strong magnetoelastic interactions. The magnetocrystalline anisotropy plays an important role in this system. Magnetic fields less than 40 kOe cannot drive either the magnetic or the crystallographic phase transition to completion for Tb5Si2.2Ge1.8 powder due to the strong single ion anisotropy of Tb.
Title: Magnetocaloric properties of Nd5Si1.45Ge2.55 compound under high hydrostatic pressure
Author(s): Skorokhod Y (Skorokhod, Y.), Arnold Z (Arnold, Z.), Kamarad J (Kamarad, J.), Morellon L (Morellon, L.), Magen C (Magen, C.)
Source: HIGH PRESSURE RESEARCH 26 (4): 495-498 DEC 2006
Abstract: The magnetic and magnetocaloric properties of Nd5Si1.45Ge2.55 compound has been studied under high hydrostatic pressure up to 0.9 GPa. At ambient pressure, the Curie temperature (T-C) and magnetocaloric effect (MCE) give values T-C = 58.1 K and -Delta S-M = 4.9 J/kg K. Both T-C and NICE weakly increase with pressure. Using the value of compressibility (1.7* 10(-2) GPa(-1)), we showed that the values of dT(C)/dV and d| - Delta S-M|/dV obtained from experiments under high pressure are sufficiently lower than those estimated from the x-dependence of the lattice cell volume of Nd-5(SixGe1-x)(4) compounds. It indicated that the changes of magnetocaloric properties cannot be explained only by volume effect.
Title: Entropy change upon magnetic field and pressure variations
Author(s): de Oliveira NA (de Oliveira, N. A.)
Source: APPLIED PHYSICS LETTERS 90 (5): Art. No. 052501 JAN 29 2007
Abstract: In this letter it is theoretically discussed the magnetocaloric effect under applied pressure and the barocaloric effect under applied magnetic field in compounds undergoing a first order magnetic phase transition. The theoretical findings of this letter point out that the magnetocaloric effect upon simultaneous variation of the magnetic field and pressure as well as the barocaloric effect in first order phase transition compounds can be very important for magnetic refrigeration technology.
Title: Enhanced magnetocaloric response in Cr/Mo containing Nanoperm-type amorphous alloys
Author(s): Franco V (Franco, V.), Conde CF (Conde, C. F.), Conde A (Conde, A.), Kiss LF (Kiss, L. F.)
Source: APPLIED PHYSICS LETTERS 90 (5): Art. No. 052509 JAN 29 2007
Abstract: The magnetocaloric effect of Fe76Cr8-xMoxCu1B15 (x=0,4) alloys is studied. Although the combined addition of Cr and Mo is more efficient in tuning the Curie temperature of the alloy, the Mo-free alloy presents a higher magnetocaloric response. The refrigerant capacity (RC) for the Mo-containing alloy is comparable to that of Gd5Ge1.9Si2Fe0.1 (for a field of 50 kOe, RC=273 J kg(-1) for the Mo alloy vs 240 J kg(-1) for the Gd-based one), with a larger temperature span of the optimal refrigeration cycle (250 K vs 90 K, respectively). The restriction of the temperature span to 90 K gives RC=187 J kg(-1) for the Mo alloy. A master curve behavior for the magnetic entropy change is also evidenced.
Title: Magnetocaloric properties of DyCo2-xGax alloys
Author(s): Ao WQ (Ao, W. Q.), Li JQ (Li, J. Q.), Liu FS (Liu, F. S.), Jian YX (Jian, Y. X.)
Source: SOLID STATE COMMUNICATIONS 141 (4): 219-222 JAN 2007
Abstract: The influence of the substitution of Ga atoms for Co atoms in DyCO2 compounds on magnetocaloric properties has been investigated. A series of DyCo2-xGax alloys with x = 0, 0.03, 0.06, 0.1, 0.15, and 0.2 was prepared by the arc-melting method for this investigation. Experimental results revealed that the Ga substitution for Co in DyCo2 can form a single phase with the cubic Laves phase structure up to x = 0.2. As the Ga content x increases, the lattice parameter and the Curie temperature T-c increases from 143 to 196 K linearly. The maximum magnetic entropy changes vertical bar Delta S-M,(max)vertical bar in a low field change of 0-1.5 T, increasing from 8.24 to 10.61 J/K kg when the Ga content x increases from 0 to 0.03, but decreasing gradually to 3.51 J/K kg as the Ga content further increases to x = 0.2. All the samples show a relatively large magnetic entropy change with very small hysteresis loss. (c) 2006 Elsevier Ltd. All rights reserved.
Title: A microcalorimeter for studying the magnetocaloric effect and the heat capacity in magnetic fields
Author(s): Korolev VV (Korolev, V. V.), Romanov AS (Romanov, A. S.), Aref'ev IM (Aref'ev, I. M.)
Source: RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY 80 (2): 310-312 FEB 2006
Abstract: The design of an automated microcalorimeter for determining the magnetocaloric effect and the heat capacity of suspensions and magnetic colloids in magnetic fields of from 0 to 1 T over a wide temperature range and the corresponding experimental procedure were described.
Title: Magnetocaloric effect and heat capacity of ferrimagnetic nanosystems: Magnetite-based magnetic liquids and suspensions
Author(s): Korolev VV (Korolev, V. V.), Romanov AS (Romanov, A. S.), Aref'ev IM (Aref'ev, I. M.)
Source: RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY 80 (3): 464-466 MAR 2006
Abstract: The magnetocaloric effect (MCE) and heat capacity of magnetite-based magnetic liquids and suspensions of magnetite in cyclohexane and water were studied calorimetrically at various temperatures and magnetic inductions. It was found that the magnetocaloric effect in the systems under study increases nonlinearly with the magnetic induction. In contrast to monocrystalline magnetite, the inverse temperature dependence was observed for the MCE in the nanosystems studied over the entire temperature range covered; i.e., the effect decreases with increasing temperature. It was found that the dependence of the specific heat on the magnetic induction passes through a maximum for all the systems at all temperatures tested; its height increases with the temperature. The extremal character of the dependence can be explained by the formation of chain structures of magnetite nanoparticles in the presence of a magnetic field.
Title: Microscopic magnetic properties of itinerant-electron system Hf0.8Ta0.2(Fe(1-x)co(x))(2) (x=0-0.09): A Mossbauer study
Author(s): Huang YJ (Huang, Yan-Jun), Han ZD (Han, Zhi-Da), Jiang ZY (Jiang, Zhong-Ying), Li SZ (Li, Shu-Zhen), Hsia YF (Hsia, Yuan-Fu)
Source: PHYSICA B-CONDENSED MATTER 388 (1-2): 354-358 JAN 15 2007
Abstract: The compounds of itinerant-electron system Hf0.8Ta0.2(Fe1-xCox)(2) (X = 0-0.09) were prepared. The crystal structure was examined by X-ray powder diffraction and all indicated a C14-type Laves phase structure. Mossbauer spectra were obtained for all the compounds between 20 and 390 K. The spectra for x = 0 clearly showed a transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state at about 110 K and one from paramagnetic state to AFM state at about 350 K. For x = 0.03, 0.06 and 0.09, the AFM-FM transition was not observed, and only showed a AFM+FM state below 340, 330, and 320K, respectively. It indicated that tiny substituted Co atoms would change the magnetic properties of the system, which originated from the disturbed crystal field and corresponding nonzero internal field at 2a site. (c) 2006 Elsevier B.V. All rights reserved.
Title: Measurement of pressure effects on the magnetic and the magnetocaloric properties of the intermetallic compounds DyCo2 and Er(Co1-xSix)(2)
Author(s): Singh NK (Singh, Niraj K.), Kumar P (Kumar, Pramod), Suresh KG (Suresh, K. G.), Nigam AK (Nigam, A. K.), Coelho AA (Coelho, A. A.), Gama S (Gama, S.)
Source: JOURNAL OF PHYSICS-CONDENSED MATTER 19 (3): Art. No. 036213 JAN 24 2007
Abstract: The effect of external pressure on the magnetic properties and magnetocaloric effect of polycrystalline compounds DyCo2 and Er(Co1-xSix)(2) (x = 0, 0.025 and 0.05) has been studied. The ordering temperatures of both the parent and the Si-substituted compounds are found to decrease with pressure. In all the compounds, the critical field for metamagnetic transition increases with pressure. It is seen that the magnetocaloric effect in the parent compounds is almost insensitive to pressure, while there is considerable enhancement in the case of Si-substituted compounds. Spin fluctuations arising from the magnetovolume effect play a crucial role in determining the pressure dependence of the magnetocaloric effect in these compounds. The variation of the magnetocaloric effect is explained on the basis of the Landau theory of magnetic phase transitions.
Title: Effect of Nb addition on the magnetic properties and magnetocaloric effect of CoMnSb alloy
Author(s): Li SD (Li, Shandong), Liu MM (Liu, Meimei), Yuan ZR (Yuan, Zuanru), Lu LY (Lu, LiYa), Zhang ZC (Zhang, Zhicheng), Lin YB (Lin, Yingbin), Du YW (Du, Youwei)
Source: JOURNAL OF ALLOYS AND COMPOUNDS 427 (1-2): 15-17 JAN 16 2007
Abstract: The effect of Nb addition on the magnetic properties and magnetocaloric effect (MCE) of CoNbxMn1-xSb alloys has been investigated. It has been found that the Curie temperature of CoMnSb alloy can be adjusted by Nb addition. On the other hand, Nb addition to CoMnSb alloy dramatically influences the magnetic properties and the MCE of CoMnSb alloy. For example, with the increase of Nb content, the saturation magnetization decreases linearly, and the transition of magnetization with temperature turns to smoother. These facts result in a reduction of magnetic entropy change, but a broader working temperature span. (c) 2006 Elsevier B.V. All rights reserved.
Title: Mossbauer study of the spin reorientation in pseudobinary alloy Hf0.82Ta0.18Fe2
Author(s): Huang YJ (Huang, Yan-Jun), Li SZ (Li, Shu-Zhen), Han ZD (Han, Zhi-Da), Wang WX (Wang, Wei-Xing), Jiang ZY (Jiang, Zhong-Ying), Huang SL (Huang, Song-Lin), Lin J (Lin, Jun), Hsia YF (Hsia, Yuan-Fu)
Abstract: Hf(1-x)Tq(x)Fe(2) pseudobinary alloy with x=0.18 was prepared. It was found to crystallize in C14 type Laves phase structure examined by Xray diffraction (XRD). Mossbauer spectra at varied temperatures show there are two transition temperatures, one for paramagnetic (PM) to antiferromagnetic (AFM) state at about 330 K, and the other for AFM to ferromagnetic (FM) state at about 180 K. In the latter transition, spin reorientation is observed. The spin of Fe magnetic moment at 6h is along c axis in AFM state while lie close to ab-plane in FM state. No magnetic interaction at 2a site is found in AFM state but FM. The hypertime field anisotropy at 6h site in FM state is also analyzed. (c) 2006 Elsevier B.V. All rights reserved.
Title: Magnetic and magnetocaloric properties of SmxGd1-xMn2Si2
Author(s): Kumar P (Kumar, Pramod), Singh NK (Singh, Niraj K.), Suresh KG (Suresh, K. G.), Nigam AK (Nigam, A. K.)
Source: JOURNAL OF ALLOYS AND COMPOUNDS 427 (1-2): 42-45 JAN 16 2007
Abstract: The magnetic and magnetocaloric properties of Gd1-xSmxMn2Si2 compounds with 0 < x <= I have been studied to determine their suitability as magnetic refrigerant materials. The rare earth ordering temperatures are found to decrease from 60 K for x = 0 to 37 K for x = 1. The temperature variations of magnetization under 'field-cooled' and 'zero-field-cooled' conditions are found to differ slightly, indicating a small thermomagnetic irreversibility. Magnetocaloric effect is calculated in terms of isothermal magnetic entropy change (Delta S-M) using the magnetization isotherms. The maximum values of Delta S-M are found to be 5.9 J kg(-1) K-1 in GdMn2Si2, and 3.4 J kg(-1) K-1 in SmMn2Si2. (c) 2006 Elsevier B.V. All rights reserved.
Title: Magnetic phase transition and magnetocaloric effect in (Gd1-xTbx)(5)Si1.72Ge2.28 compounds
Author(s): Deng JQ (Deng, J. Q.), Zhuang YH (Zhuang, Y. H.), Li JQ (Li, J. Q.), Zhou KW (Zhou, K. W.)
Source: JOURNAL OF ALLOYS AND COMPOUNDS 428 (1-2): 28-33 JAN 31 2007
Abstract: The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric proper-ties for the (Gd1-xTbx)(5)Si1.72Ge2.28 compounds with x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 have been investigated by X-ray powder diffraction and magnetization measurement. A small amount of the Tb substitution in Gd5Si1.72Ge2.28 compound can remain its first order magnetic-crystallographic transition and enhance its magnetic entropy change significantly, although have the negative influence on the compound Curie temperature T-c. The influence of the applied magnetic field on transition temperature also was discussed. The maximum magnetic entropy changes in the low magnetic field change of 2.0 T for the (Gd0.94Tb0.06)(5)Si1.72Ge2.28, sample reaches 25.13 J kg(-1) K-1, much lager than that of pure Gd5Si1.78Ge2.28 compound (13.73 J kg(-1) K-1 at 247 K) in this work. (c) 2006 Elsevier B.V. All rights reserved.
Title: Low-field inverse magnetocaloric effect in Ni50-xMn39+xSn11 Heusler alloys
Author(s): Han ZD (Han, Z. D.), Wang DH (Wang, D. H.), Zhang CL (Zhang, C. L.), Xuan HC (Xuan, H. C.), Gu BX (Gu, B. X.), Du YW (Du, Y. W.)
Source: APPLIED PHYSICS LETTERS 90 (4): Art. No. 042507 JAN 22 2007
Abstract: The low-field magnetic entropy changes in Ni50-xMn39+xSn11 alloys (x=5, 6, and 7) were investigated. The martensitic transition shifts to lower temperature with the increase of Mn concentration. Under an applied magnetic field of 10 kOe, the magnetic entropy changes are 6.8, 10.1, and 10.4 J/kg K, for x=5, 6, and 7, respectively. The large entropy change in Ni50-xMn39+xSn11 can be attributed to the sharp magnetization change associated with the martensitic transition from a ferromagnetic parent phase to a weak-magnetic martensitic phase. The large low-field magnetic entropy change and low cost suggest Ni50-xMn39+xSn11 alloy as the promising magnetic refrigerant. (c) 2007 American Institute of Physics.
Title: Giant magnetocaloric effect in epsilon-(Mn0.83Fe0.17)(3.25)Ge antiferromagnet
Author(s): Du J (Du, J.), Cui WB (Cui, W. B.), Zhang Q (Zhang, Q.), Ma S (Ma, S.), Xiong DK (Xiong, D. K.), Zhang ZD (Zhang, Z. D.)
Source: APPLIED PHYSICS LETTERS 90 (4): Art. No. 042510 JAN 22 2007
Abstract: The magnetic phase transition and magnetocaloric effect are investigated on epsilon-(Mn0.83Fe0.17)(3.25)Ge compound. A large positive magnetic entropy change Delta S-M is observed, which is accompanied with a field-induced metamagnetic transition from a collinear to a triangular antiferromagnetic configuration in this antiferromagnetic compound. The maximum value of Delta S-M is 11.6 J/kg K at 93 K for a magnetic field change of 7 T. The study on systems with antiferromagnetic phases may open an important field in searching new materials for magnetic refrigeration. (c) 2007 American Institute of Physics.
Title: Effect of Ge substitution for Si on the anomalous magnetocaloric and magnetoresistance properties of GdMn2Si2 compounds
Author(s): Kumar P (Kumar, Pramod), Singh NK (Singh, Niraj K.), Suresh KG (Suresh, K. G.), Nigam AK (Nigam, A. K.), Malik SK (Malik, S. K.)
Source: JOURNAL OF APPLIED PHYSICS 101 (1): Art. No. 013908 JAN 1 2007
Abstract: The effect of Ge substitution on the magnetization, heat capacity, magnetocaloric effect, and magnetoresistance of GdMn2Si2-xGex (x=0, 1, and 2) compounds has been studied. The magnetic transition associated with the Gd ordering is found to change from second order to first order on Ge substitution. Magnetic contributions to the total heat capacity and the entropy have been estimated. Magnetocaloric effect has been calculated in terms of adiabatic temperature change (Delta T-ad) as well as isothermal magnetic entropy change (Delta S-M) using the heat capacity data. The temperature dependence of the magnetocaloric effect in all the three compounds have shown broad peaks. The maximum values of Delta S-M and Delta T-ad for GdMn2Ge2 are found to be 5.9 J/kg K and 1.2 K, respectively. The magnetoresistance is found to be very large and positive with a maximum value of about 22% in the case of GdMn2Ge2. In the other two compounds also, the magnetoresistance is predominantly positive, except in the vicinity of the Gd ordering temperature. The anomalous nature of the magnetocaloric effect and the magnetoresistance has been attributed to the canted magnetic structure of these compounds. (c) 2007 American Institute of Physics.
Title: The structure and magnetocaloric effect of rapidly quenched Gd5Si2Ge2 alloy with low-purity gadolinium
Author(s): Zhang TB (Zhang, Tiebang), Chen YG (Chen, Yungui), Teng BH (Teng, Baohua), Tang YB (Tang, Yongbai), Fu H (Fu, Hao), Tu MJ (Tu, Mingjing)
Source: MATERIALS LETTERS 61 (2): 440-443 JAN 2007
Abstract: A magnetic refrigerating material Gd5Si2Ge2 was prepared by arc-melting method under argon atmosphere with low-purity commercial gadolinium. The structure and magnetocaloric effect (MCE) of the as-east and rapidly quenched Gd5Si2Ge2 alloys were investigated by means of Xray diffraction and magnetic measurements. The as-cast Gd5Si2Ge2 consists of Gd5Si2Ge2-type, Gd5Si4-type, Gd-5(Si,Ge)(3) and Gd(Si,Ge) phases from powder XRD results. The alloys quenched at a velocity of 25 m/s or 40 m/s both adopt in a single phase with orthorhombic Gd5Si4-type structure. The lattice parameters under different quenched velocities calculated by least-squares method have no significant difference. After being rapidly quenched at 40 m/s, the Curie temperature of Gd5Si2Ge2 is about 303 K and its maximum magnetic entropy change is 7.25 J/kg K (0-5 T). (c) 2006 Elsevier B.V. All rights reserved.
Title: Rare earths and magnetic refrigeration
Author(s): Gschneidner KA (Gschneidner, Karl A., Jr.), Pecharsky VK (Pecharsky, Vitalij K.)
Source: JOURNAL OF RARE EARTHS 24 (6): 641-647 DEC 2006
Abstract: Magnetic refrigeration is a revolutionary, efficient, environmentally friendly cooling technology, which is on the threshold of commercialization. The magnetic rare earth materials are utilized as the magnetic refrigerants in most cooling devices, and for many cooling application the Nd2Fe14B permanent magnets are employed as the source of the magnetic field. The status of the near room temperature magnetic cooling was reviewed.
Title: Advanced magnetocaloric materials: What does the future hold?
Author(s): Pecharsky VK (Pecharsky, Vitalij K.), Gschneidner KA (Gschneidner, Karl A., Jr.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1239-1249 DEC 2006
Abstract: Recent achievements in the design of robust near room temperature magnetic cooling devices signify paradigm shift in refrigeration, liquefaction and freezing technologies, and call for a much broader base of advanced magnetocaloric materials to support quick materialization of this environmentally friendly, energy efficient technology in a variety of markets. The latest material discoveries are reviewed and current trends in engineering of advanced magnetocaloric compounds have been identified. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Experimental investigation on refrigeration performance of a reciprocating active magnetic regenerator of room temperature magnetic refrigeration
Author(s): Gao Q (Gao, Q.), Yu BF (Yu, B. F.), Wang CF (Wang, C. F.), Zhang B (Zhang, B.), Yang DX (Yang, D. X.), Zhang Y (Zhang, Y.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1274-1285 DEC 2006
Abstract: Room temperature magnetic refrigeration has been proved to be a feasible refrigerating technology and has a prosperous application potential. In this research, magnetocaloric effect (MCE) of metal gadolinium is measured and the metal is prepared from ingot to granular state by method of hydriding-ball milling-dehydriding. The other compound, Gd5Si2Ge2 alloy, is also prepared into grains by mechanical comminuting and its magnetocaloric property is obtained. An experimental system of room temperature magnetic refrigeration is established, and three kinds of magnetic refrigerant (MR I: 0.3 mm mean diameter gadolinium particle, MR II: 0.55 mm mean diameter gadolinium particle and MR III: 0.3-0.75 mm Gd5Si2Ge2 alloy particle) are employed in AMR. Performance experiments of AMR system under various temperature range, temperature span, flow rate, and flow period conditions are investigated. The results indicate that AMR adopting MR I, II, III can generate a maximum refrigerating capacity of 18.7 W, 17.8 W, and 10.3 W, respectively, under a 3 K temperature span. With the increasing temperature span, the capacity decreases. MR I and MR II have an equivalent refrigerating ability higher than MR III. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Experimental investigation of a three-material layered active magnetic regenerator
Author(s): Rowe A (Rowe, A.), Tura A (Tura, A.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1286-1293 DEC 2006
Abstract: This work reports on experimental studies using an active magnetic regenerative test apparatus (AMRTA) in near room-temperature refrigeration cycles. Experiments using regenerator beds composed of three different magnetocaloric materials combined in a layered configuration with applied fields of 2 T have produced no-load temperature spans in excess of 50 K. The test apparatus uses two active magnetic regenerators each containing approximately 135 g of refrigerant. An overview of the test apparatus, operating parameters, and performance is described. The impacts of operation at varying heat rejection temperatures, applied fields of 1.5 T and frequencies between 0.65 and 1.0 Hz are presented. In addition, the impacts of operating pressure and applied load on temperature spans are discussed. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Design and performance of a permanent-magnet rotary refrigerator
Author(s): Zimm C (Zimm, C.), Boeder A (Boeder, A.), Chell J (Chell, J.), Sternberg A (Sternberg, A.), Fujita A (Fujita, A.), Fujieda S (Fujieda, S.), Fukamichi K (Fukamichi, K.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1302-1306 DEC 2006
Abstract: In order to demonstrate the potential of magnetic refrigeration to provide useful cooling near room temperature, Astronautics Corporation of America constructed a rotary magnetic refrigerator (RMR) in 2001. The RMR uses the active magnetic regenerator (AMR) cycle with an aqueous heat transfer fluid. The required change in magnetic field is produced by the rotation of a wheel packed with porous beds of magnetocaloric material through a 1.5 T Nd2Fe14B permanent magnet with steel flux concentration poles. A pump, and valves mounted to the wheel, control heat transfer fluid flow through the magnetocaloric beds and heat exchangers. This rotary design allows quiet, reliable operation over a range of frequencies (0.5-4 Hz), heat transfer fluid flow rates and cooling power. The performance of the device using Gd and Gd alloy spherical particles is reported and analyzed. We also describe the performance effects of introducing layered beds and an La(Fe1-xSix)(13)H-y alloy with a first order magnetic transition. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Performance analysis of a room temperature rotary magnetic refrigerator for two different gadolinium compounds
Author(s): Tagliafico LA (Tagliafico, L. A.), Scarpa F (Scarpa, F.), Canepa F (Canepa, F.), Cirafici S (Cirafici, S.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1307-1317 DEC 2006
Abstract: A thermodynamic performance analysis is developed for a Steyert-like rotary magnetic refrigeration (RMR) system operating in the near-room temperature range with two possible, alternative, gadolinium compounds. The first magnetocaloric material (MCM) is an alloy (Gd7Pd3) with a well defined Curie temperature (around 318 K), while the second MCM (Gd76Pd24) is an eutectic compound with a smoothed double Curie transition (at 298 and 318 K, respectively).
The main issues linked to the thermodynamic properties of the magnetic material are outlined and the influence of the magnetocaloric properties on the global performance (useful effect, coefficient of performance, and so on) of the refrigeration system is discussed. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Innovative design of a magnetocaloric system
Author(s): Vasile C (Vasile, C.), Muller C (Muller, C.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1318-1326 DEC 2006
Abstract: In the present paper we consider the problem of optimizing the cooling of a magnetocaloric refrigerator. In this work we first theoretically and then experimentally study the performance of a single material regenerator under different operating conditions. The basic principles of the design and implementation of our magnetic refrigerator prototype are presented as well as a new magnetic assembly of NdFeB permanent magnets.
The design of the equipment uses a movement of relative displacement optimized for the phases of activation and inactivation of the magnetic field. Each part of the equipment is implemented in order to be controlled separately and to allow a large variety of the tests: gear pumps with individual control, sequence of programmable magnetocaloric cycle, unit control by programmable controller and application programming interface by color LCD touch screen, real-time processing data acquisition using a National Instruments System implemented on Independent PC, expelled heat using different standard heat exchangers. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: A magnetic field source system for magnetic refrigeration and its interaction with magnetocaloric material
Author(s): Allab F (Allab, F.), Kedous-Lebouc A (Kedous-Lebouc, A.), Yonnet JP (Yonnet, J. P.), Fournier JM (Fournier, J. M.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1340-1347 DEC 2006
Abstract: The magnetic field source system constitutes an important component of magnetic refrigeration. A specific methodology for its' dimensioning is proposed in this paper. It is based on analytical calculation models and takes into account the geometry of the system, the magnetic properties of the magnetocaloric material and the magnetothermal cycle (direct or active magnetic regenerative refrigeration). The analytical calculation of the field is first developed and applied to usual permanent magnet-based field sources with and without soft magnetic materials. Then the forces generated by the interaction between the field and the magnetocaloric effect material are analytically evaluated considering the real field distribution. All calculations are validated thanks to two- or three-dimensional finite element method simulations. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Research on performance of regenerative room temperature magnetic refrigeration cycle
Author(s): Yu BF (Yu Bingfeng), Zhang Y (Zhang Yan), Gao Q (Gao Qiang), Yang DX (Yang Dexi)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1348-1357 DEC 2006
Abstract: On the basis of classical Langevin theory along with statistical mechanics, thermodynamics and magnetism, a new expression of magnetocaloric parameters used for room temperature magnetic refrigeration is proposed, which is briefer and more accurate than the existing one, providing a new way for studying performance of regenerative room temperature magnetic Ericsson refrigeration cycle. Influences of temperature of heat reservoirs and magnetic intensity on cycle refrigeration capacity and coefficient of performance are analyzed. The results show that the maximal temperature span of the cycle increases but its increasing rate decreases with the increase of magnetic field strength. In addition, there exists only one maximum value of effective refrigerating capacity. Two cycles with the same COP can reach a same temperature span under a certain magnetic field strength. A large magnetic field strength can improve COP but the increase rate of COP decreases. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Potential for cost effective magnetocaloric air conditioning systems
Author(s): Russek SL (Russek, Steven L.), Zimm CB (Zimm, Carl B.)
Source: INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 29 (8): 1366-1373 DEC 2006
Abstract: Magnetic refrigeration is an emerging technology that exploits the magnetocaloric effect found in solid-state refrigerants. The combination of solid-state refrigerants, water-based heat transfer fluids, and high efficiency will lead to environmentally desirable products with minimal contributions to global warming. Among the numerous applications of refrigeration technology, air conditioning applications provide the largest aggregate cooling power and use the greatest quantity of electric energy. The primacy of the air conditioning application makes the establishment of cost targets for this application an essential feature of the R&D plan for magnetic refrigeration technology. A preliminary assessment of the permanent magnet costs and magnetocaloric material costs indicates that, for suitably chosen materials and operating conditions, these costs lay well below the total manufactured costs for vapor compression based air conditioners. (c) 2006 Elsevier Ltd and IIR. All rights reserved.
Title: Negative magnetocaloric effect from highly sensitive metamagnetism in CoMnSi1-xGex
Author(s): Sandeman KG (Sandeman, K. G.), Daou R (Daou, R.), Ozcan S (Ozcan, S.), Durrell JH (Durrell, J. H.), Mathur ND (Mathur, N. D.), Fray DJ (Fray, D. J.)
Source: PHYSICAL REVIEW B 74 (22): Art. No. 224436 DEC 2006
Abstract: We report a negative magnetocaloric effect in CoMnSi1-xGex arising from a metamagnetic magnetoelastic transition. The effect is of relevance to magnetic refrigeration over a wide range of temperature, including room temperature. In addition we report a very high shift in the metamagnetic transition temperature with applied magnetic field. This is driven by competition between antiferromagnetic and ferromagnetic order which can be readily tuned by applied pressure and compositional changes.
Title: Magnetic properties and magnetocaloric effects in Mn1.2Fe0.8P1-xGex compounds
Author(s): Ou ZQ (Ou, Z. Q.), Wang GF (Wang, G. F.), Lin S (Lin, Song), Tegus O (Tegus, O.), Bruck E (Bruck, E.), Buschow KJ (Buschow, Kh J.)
Source: JOURNAL OF PHYSICS-CONDENSED MATTER 18 (50): 11577-11584 DEC 20 2006
Abstract: We have studied the magnetic properties and magnetocaloric effects in the Mn1.2Fe0.8P1-xGex compounds with x = 0.2, 0.22, 0.3, 0.4 and 0.5. X-ray diffraction patterns show that the Mn1.2Fe0.8P1-xGex compounds crystallize in the hexagonal Fe2P-type crystal structure. The magnetic moments of the Mn1.2Fe0.8P1-xGex compounds measured at 5 K and 5 T increase with increasing Ge content. The Curie temperature increases strongly and the magnetic entropy change has a maximum around 233 K for the compound with x = 0.22, which is about 19 and 31 J kg(-1) K-1 for a field change of 2 and 5 T, respectively.
Title: Giant magnetic entropy change in La0.7Ca0.3MnO3 in low magnetic field
Author(s): Ulyanov AN (Ulyanov, A. N.), Kim JS (Kim, J. S.), Shin GM (Shin, G. M.), Kang YM (Kang, Y. M.), Yoo SI (Yoo, S. I.)
Source: JOURNAL OF PHYSICS D-APPLIED PHYSICS 40 (1): 123-126 JAN 7 2007
Abstract: A giant magnetocaloric effect was found in La0.7Ca0.3MnO3 manganite at low magnetic fields. The magnetic entropy changes caused by a magnetic field change of 0.5 and 1.0 T were as large as 5.04 and 6.25 J kg(-1) K-1, respectively, which exceed those of perovskite-like magnetic refrigerants or elemental Gd by a factor of 2-3. The extremely high values of the magnetocaloric effect are attributed to a sharp drop in the magnetization at a first-order ferromagnetic-paramagnetic phase transition and S-shaped magnetization versus field dependence.
Title: First order magneto-structural transition in functional magnetic materials: phase-coexistence and metastability
Author(s): Roy SB (Roy, S. B.), Chattopadhyay MK (Chattopadhyay, M. K.), Manekar MA (Manekar, M. A.), Sokhey KJS (Sokhey, K. J. S.), Chaddah P (Chaddah, P.)
Source: BULLETIN OF MATERIALS SCIENCE 29 (6): 623-631 NOV 2006
Abstract: First order magneto-structural transition plays an important role in the functionality of various magnetic materials of current interest like manganese oxide systems showing colossal magnetoresistance, Gd-5(Ge, Si)(4) alloys showing giant magnetocaloric effects and magnetic shape memory alloys. The key features of this magneto-structural transition are phase-coexistence and metastability. This generality is highlighted with experimental results obtained in a particular class of materials. A generalized framework of disorder influenced first order phase transition is introduced to understand the interesting experimental results which have some bearing on the functionality of the concerned materials.
Title: Structure and magnetocaloric effect in melt-spun La (Fe, Si)(13) and MnFePGe compounds
Author(s): Yan A (Yan Aru)
Source: RARE METALS 25: 544-549 Sp. Iss. SI, OCT 2006
Abstract: The magnetocaloric properties of melt-spun La(Fe, Si)(13) and MnFePGe compounds were investigated. Very large value of magnetic entropy change vertical bar Delta S vertical bar = 31 and 35.4 J center dot(kg center dot K)(-1) under 5 T were obtained at 201 K in LaFe11.8Si1.2 melt-spun ribbons and at around 317 K in Mn1.1Fe0.9P0.76Ge0.24 melt-spun ribbons, respectively. The large magnetocaloric effect results from a more homogenous element distribution related to the very high cooling rate during melt-spinning. The excellent MCE properties, the low materials cost and the accelerated aging regime make the melt-spun-type La(Fe, Si)(13) and MnFePGe materials an excellent candidate for magnetic refrigerant applications.
Title: Magnetic properties of Nd12Co6Pb compound
Author(s): He W (He Wei), Zhang JL (Zhang Jiliang), Zeng LM (Zeng Lingmin)
Source: JOURNAL OF RARE EARTHS 24: 329-331 Sp. Iss. SI, DEC 2006
Abstract: The magnetic and magnetocaloric properties for the Nd12Co6Pb compound were investigated. The Curie temperature T-C of the magnetic transition of Nd12Co6Pb compound is 194 K. The experimentally determined magnetic effective paramagnetic moment is mu(eff) = 12.36 mu(B) per formula unit (3.49 mu(B) per Nd atom). The maximum magnetic entropy change in the low magnetic field changes of 0 similar to 2 T for the Nd12Co6Pb compound is about 215.0 J center dot mole(-1) center dot K-1.
Title: Magnetocaloric properties of the pseudo-binary Er-rich lanthanide dialuminide compounds
Author(s): Lima AL (Lima, A. L.)
Source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 310 (1): 51-56 MAR 2007
Abstract: The compounds (RE1-xErx)Al-2 (where RE = Gd, Ho, Pr for x >= 0.75) were studied experimentally and theoretically in order to evaluate their magnetocaloric properties and suitability for use as working media in magnetic refrigeration devices operating at low temperatures. I propose a theoretical description of these systems which are composed of two rare-earth ions with different total angular momentum (J(RE)(1) and J(RE)(2)) Our model Hamiltonian is solved self-consistently, taking into account crystal electric fields, exchange interactions, the Zeeman effect and second-order effects. From the eigenvalues and eigenstates, the partition function from which thermodynamic quantities may be calculated is obtained, including the isothermal magnetic entropy change, Delta S-mag. In order to validate the theoretical results, Delta S(ma)g obtained from heat capacity measurements using Maxwell's relations is compared to the calculated one. The results indicate that for Er-rich compositions fairly good agreement between theoretical and experimental Delta S-mag is obtained. (c) 2006 Elsevier B.V. All rights reserved.