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Journal ArticleDOI

On the feasibility of production of microkelvin temperature by nuclear demagnetisation

01 Nov 1976-Pramana (Springer Science and Business Media LLC)-Vol. 7, Iss: 5, pp 319-323
TL;DR: In this paper, an attempt has been made to show that PrBe13, a Van-Vleck paramagnet, can be used to produce a lattice temperature of 10µK. or lower.
Abstract: Nuclear demagnetisation as a means of refrigeration has been proposed and achieved long ago. In this paper an attempt has been made to show that PrBe13, a Van-Vleck paramagnet, can be used to produce a lattice temperature of 10µK. or lower. Such a calculation can be used for a computer simulation of the process.
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Book ChapterDOI
01 Jan 2021
TL;DR: The structural chemistry of beryllium intermetallic compounds is governed by the small atomic radius, low valence electron count and covalent bonding character of BER as discussed by the authors.
Abstract: The structural chemistry of beryllium intermetallic compounds is governed by the small atomic radius, low valence electron count and covalent bonding character of beryllium. The combination with the large rare earth and actinide ions leads to high coordination numbers in the MBe13 compounds, with NaZn13 structure. The cage-like structure of the beryllium framework around Ln atoms gives rise to low-energy Einstein modes in the phonon spectra. In the heavy lanthanide beryllides, the competition between indirect exchange interaction and magnetocrystalline anisotropy leads to complex helimagnetic order. The binary beryllides compounds of Ce, U and Np show heavy fermion behavior. In the ternary rare earth-beryllium compounds, beryllium can serve as interstitial atom or take the place of p-block and transition metal atoms. The rare earth-transition metal beryllides are closely related to the rare earth-iron boride phases, where beryllium can take the place of boron as well as iron in the structure. The beryllium-rich compounds typically show a high degree of high space filling and high coordination numbers for the rare earth atoms. Most beryllium-rich compounds with non-magnetic ions are superconductors with critical temperatures below 1 K.

3 citations

References
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Journal ArticleDOI
E. Bucher1, J. P. Maita1, G. W. Hull1, R. C. Fulton1, A. S. Cooper1 
TL;DR: In this paper, a magnetic study has been conducted of 17 beryllides of the form $M{\mathrm{Be}}_{13}$, $M$ being a rare earth, Th, U, and an alloy, and the expected nuclear cooling and ordering behavior is also thoroughly discussed.
Abstract: A magnetic study has been conducted of 17 beryllides of the form $M{\mathrm{Be}}_{13}$, $M$ being a rare earth, Th, U, and an alloy ${\mathrm{La}}_{0.75}$${\mathrm{Tm}}_{0.25}$. Specific-heat studies were also made for $M=\mathrm{L}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{P}\mathrm{r},\phantom{\rule{0ex}{0ex}}\mathrm{S}\mathrm{m},\phantom{\rule{0ex}{0ex}}\mathrm{T}\mathrm{m},\phantom{\rule{0ex}{0ex}}\mathrm{L}\mathrm{u},\phantom{\rule{0ex}{0ex}}\mathrm{T}\mathrm{h},\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{n}\mathrm{d}\phantom{\rule{0ex}{0ex}}\mathrm{U}$. A thorough crystal-field analysis is presented for Pr${\mathrm{Be}}_{13}$, Tm${\mathrm{Be}}_{13}$, both ions being in a crystal-field singlet ground state, and the expected nuclear cooling and ordering behavior is also thoroughly discussed.

114 citations

Journal ArticleDOI
TL;DR: In this paper, magnetic-susceptibility and specific-heat measurements in Van Vleck paramagnetic Pr${\mathrm{Cu}}_{2}$ down to 30 mK reveal that the Pr nuclei enter an antiferromagnetically ordered state below 54 mK.
Abstract: Magnetic-susceptibility and specific-heat measurements in Van Vleck paramagnetic Pr${\mathrm{Cu}}_{2}$ down to 30 mK reveal that the Pr nuclei enter an antiferromagnetically ordered state below 54 mK. This high nuclear ordering temperature results from magnetic exchange interactions between the Pr ions, which must be close to the critical value necessary for spontaneous electronic magnetic order in this compound.

54 citations

Journal ArticleDOI
TL;DR: In this paper, the quadrupole relaxation rate τQ-1 in these metals, except in Tl, could be observed as the dominant contribution to the total rate at lower temperatures.
Abstract: Perturbed angular distribution methods (PAD) following nuclear reactions were applied to relaxation phenomena of excited nuclear states in liquid Ga, In, InGa alloys, Te, Hg, Tl, and Pb. Due to the selection of excited states with small g-factors the quadrupole relaxation rate τQ-1 in these metals, except in Tl, could be observed as the dominant contribution to the total rate at lower temperatures. It is suggested that the τQ-1 rates in Ga, In, InGa and Hg are essentially due to the diffusion induced mechanism while the interpretation of τQ-1 in Pb and Te is more complicated. Further magnetic relaxation rates of isolated impurities are deduced for four systems and quadrupole moments of ms-states in 71Ge, 115Sn, 205Pb, and 206Pb are derived from the quadrupole relaxation rates.

47 citations

Journal ArticleDOI
TL;DR: In this paper, a conduction electron temperature of 0.37 mK, significantly lower than before, was achieved, and the nuclear stage could be kept below 2 mK for 12 hours.

24 citations