Magnetocaloric effects of ferromagnetic erbium mononitride

Nakagawa, Takashi; Arakawa, Takayuki; Sako, Kengo; Tomioka, Naoto; Yamamoto, Takao A.; Kusunose, Takafumi; Niihara, Koichi; Kamiya, Kōji; Numazawa, Takenori

doi:10.1016/j.jallcom.2005.04.061

Cited by 31 publications

(12 citation statements)

References 12 publications

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“…Like other RE nitrides ErN is 9,36 characterized by ionic bonding; however, the equilibrium distance 41 11 , with a full f semishell containing seven spin up electrons and an half filled f semishell containing four spin down electrons. This was verified with all spinresolved approaches implemented in DFTB.…”

Section: A Ernmentioning

confidence: 96%

“…We test our methods on both a bulk RE compound and RE impurities: We choose ErN as representative of the first class of systems and Er Ga in GaN as representative of the second. Both examples are relevant for technological applications: ErN has been recently suggested as an ideal magnetic refrigerator and regenerator for cryogenic applications 10,11 and as basis for spin filter devices ͑because of its half metallicity͒, while Er-doped GaN samples have been successfully exploited ͑because of the sharp intra-f optical transitions͒ for both the 1.54 m telecommunications frequency and as a primary color emitter ͑green͒ in thin film electroluminescent phosphor systems. 12 More generally, rare earths are also promising candidates for the realization of high T c semiconductor spintronic devices.…”

Section: Introductionmentioning

confidence: 99%

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Efficient tight-binding approach for the study of strongly correlated systems

et al. 2007

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In this work, we present results from self-consistent charge density functional based tight-binding ͑DFTB͒ calculational scheme, including local-density approximation +U ͑LDA+U͒ and simplified self-interactioncorrected-like potentials for the simulation of systems with localized strongly correlated electrons. This approach attempts to combine the efficiency of tight binding with the accuracy of more sophisticated ab initio methods and allows treatment of highly correlated electrons for very large systems. This is particularly interesting for the case of rare earths in GaN, where dilute amount of rare earth ions is used. In this work, we show the results of test calculations on bulk ErN and on the substitutional Er Ga in wurtzite GaN, which we choose as representatives of bulk and point defects in solids with strongly correlated electrons. We find that ErN is a half metal in the ferromagnetic phase and that the substitutional Er Ga in wurtzite GaN has C 3v symmetry. These examples show that the DFTB approach reproduces well the results of more demanding calculation schemes with a very low computational cost, making it suitable for the study of extended systems beyond the capabilities of density functional theory.

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Section: A Ernmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Efficient tight-binding approach for the study of strongly correlated systems

et al. 2007

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“…The magnetic refrigeration is based on a physical phenomenon, magnetocaloric effect, and promising cooling technology especially at cryogenic temperatures [4,5]. Therefore, the rare-earth mononitirides would be promising materials applicable (i) to the magnetic cooling and liquefaction of hydrogen occurring at 20 K from the liquid nitrogen temperature, and (ii) to the regenerator used under 20 K. We have synthesized mononitrides of Gd [6,9], Tb [7,9], Dy [6], Ho [7], Er [8] and binary solid solutions thereof, Gd-Dy [6], Gd-Tb [9], Tb-Ho [9], by the carbothermic reduction (CTR) method, and demonstrated that their magnetic entropy changes S accompanied with the ferro-para transition are larger than those of the other candidate materials of the second-order magnetic phase transition (SOMT). The SOMT material experiences no structural change induced by the iterative magnetize-demagnetize operation and is free from material degradation as experienced by materials of the first-order magnetic phase transition.…”

Section: Introductionmentioning

confidence: 99%

Magnetocaloric effect, specific heat and adiabatic temperature change of HoxEr1−xN (x=0.25, 0.5, 0.75)

Hirayama

Tomioka

Nishio

et al. 2008

Journal of Alloys and Compounds

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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%

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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Magnetocaloric effects of ferromagnetic erbium mononitride

Cited by 31 publications

References 12 publications

Efficient tight-binding approach for the study of strongly correlated systems

Efficient tight-binding approach for the study of strongly correlated systems

Magnetocaloric effect, specific heat and adiabatic temperature change of HoxEr1−xN (x=0.25, 0.5, 0.75)

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

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