The Specific Heat of HoCu2 in Magnetic Fields

Bischof, J.; Diviš, M.; Svoboda, P.; Smetana, Z.

doi:10.1002/pssa.2211140264

Cited by 11 publications

(3 citation statements)

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“…The compound crystallizes in the orthorhombic CeCu 2 -type structure (space group ¼ Imma), which can be described as a stacking of alternating layers of Ho and Cu atoms along the c axis of the crystal. 16 Heat capacity, magnetization, and electric transport studies indicate that the compound orders antiferromagnetically below T N ¼ 10.5 K and a second magnetic anomaly is observed at T t ¼ 7.4 K. [17][18][19] Powder neutron diffraction studies indicate that HoCu 2 attains an incommensurately modulated non-collinear magnetic structure below T t . [20][21][22] Signature of metamagnetic transition was reported for the compound at 4.2 K. 18 Our investigation indicates significantly large MCE in the sample (DS ¼ À19.3 J kg À1 K À1 around 10.5 K for H: 0-50 kOe).…”

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confidence: 97%

Observation of large low temperature magnetocaloric effect in HoCu2

Karmakar

Giri

Majumdar

2015

Journal of Applied Physics

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Articles you may be interested inMagnetic properties and magnetocaloric effect in the RCu2Si2 and RCu2Ge2 (R = Ho, Er) compounds J. Appl. Phys. 115, 073905 (2014); 10.1063/1.4864419 Low-temperature large reversible magnetocaloric effects of ErNi 1-x Cu x Al (x = 0.2, 0.5, 0.8) intermetallic compounds J. Appl. Phys. 114, 213907 (2013); 10.1063/1.4838040 Low-temperature reversible giant magnetocaloric effect in the HoCuAl compound Low hysteresis and large room temperature magnetocaloric effect of Gd5Si2.05− x Ge1.95− x Ni2 x (2x = 0.08, 0.1) alloys J. Appl. Phys. 113, 17A916 (2013); 10.1063/1.4795434 Giant reversible magnetocaloric effect in metamagnetic HoCuSi compound Appl. Phys. Lett. 96, 152501 (2010);We report the observation of large low temperature magnetocaloric effect and magnetoresistance in the rare-earth based intermetallic compound HoCu 2 . The compound undergoes an antiferromagnetic type ordering below about T N ¼ 10.5 K, which is second order in nature. The magnetocaloric effect in terms of entropy change under the application of 50 kOe of field is found to have a maximum value of À19.3 J kg À1 K À1 peaking around T N , and an appreciable value of relative cooling power of 268 J kg À1 was associated with it. The sample also shows giant negative magnetoresistance with its value as high as À36.5% around T N for 50 kOe of field. Field induced second order metamagnetic transition is found to be responsible for the observed magnetocaloric and magnetoresistance behaviors in the sample. The sample is devoid of any thermal or field hysteresis by virtue of the second order nature of the transitions, which enables us to exploit large reversible magnetic cooling at cryogenic temperatures. V C 2015 AIP Publishing LLC.

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Section: Introductionmentioning

confidence: 97%

Observation of large low temperature magnetocaloric effect in HoCu2

Karmakar

Giri

Majumdar

2015

Journal of Applied Physics

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“…The most important requirement for the regenerator materials are large specific heat around the working temperatures. To improve the efficiency, the researchers and engineers are seeking advanced regenerator materials [1][2][3][4] We have reported rare earth nitrides (ErN, HoN, DyN, TbN and GdN) have large specific heat at cryogenic temperatures [5,6]. Among them, ErN shows a peak of specific heat at 4 K. Thus, ErN was expected to be suitable materials for second stage regenerator of 4 K GM cryocoolers.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of loading ratio of ErN as regenerator of 4K-GM cryocooler

Nakagawa

Miyauchi

Shiraishi

et al. 2017

J. Phys.: Conf. Ser.

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Abstract. High purity erbium nitride (ErN) spheres with the size range of 150-180 Pm and 180-212 Pm were prepared by nitriding Er metal spheres with low oxygen content. The initial regenerator material of HoCu2 on the cold end of the second regenerator column in 4K-GM cryocooler with nominal cooling power of 0.1 W at 4.2 K was replaced by ErN with different sizes. Higher cooling power was obtained when ErN of smaller size with lower oxygen content was used. We investigated the effect of partial replacement of HoCu2 by ErN in the cold end side of second stage regenerator column on cooling power of 4K-GM cryocoolers. When ErN were substituted for 20 % of HoCu2, the cooling power at 4.2 K reached 0.318 W. This value was 1.36 times as high as that of the cooling power of the GM cryocooler with commercially available regenerator arrangement. Therefore, use of ErN regenerator materials leads to the energy-saving and downsizing of 4K-GM cryocoolers. IntroductionGifford-McMahon (GM) cryocoolers are typical 4 K cryogenic refrigerators widely used for ultra high vacuum pumps, helium and hydrogen liquefaction, and for systems using superconducting magnets such as magnetic resonance imaging diagnosis devices and magnetic levitation trains. However, to obtain 1 W of cooling power at 4.2 K using GM cryocoolers, input power as much as several kW is needed. It is a very important problem to enhance their performances at cryogenic temperatures from the view of the energy saving. The 4K-GM cryocoolers have 2 stages of regenerators. By repeating compress and expansion of helium gas, cryogenic temperate is formed. The first-stage regenerator consists of stacked copper meshes, and the second consists of packed Pb and HoCu2 spheres. The performance and efficiency of the 4K-GM cryocoolers depend on the second stage regenerator materials. The most important requirement for the regenerator materials are large specific heat around the working temperatures. To improve the efficiency, the researchers and engineers are seeking advanced regenerator materials [1][2][3][4].

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