Nuclear Magnetic Ordering in Pr<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ni</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>at 0.4 mK

Kubota, Minoru; Folle, H. R.; Buchal, Ch.; Mueller, R. M.; Pobell, F.

doi:10.1103/physrevlett.45.1812

Cited by 104 publications

(24 citation statements)

References 16 publications

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“…We can study both nuclear ferromagnets and antiferromagnets in these Pr compounds by changing atomic species bound to Pr atoms and the anisotropy effect by selecting crystal structures. Moreover, we can investigate the nuclear ordering transition not only by measuring physical properties of nuclear spins (such as PrNi 5 , PrCu 6 , PrIn 3 , PrBe 13 ) [4][5][6][7][8][9] but also by examining electronic properties [10][11][12].…”

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confidence: 99%

Critical Behavior of Susceptibility at the Nuclear Ordering Transition inPrCu6

Akashi¹,

Kawabata²,

Matsubara³

et al. 1999

Phys. Rev. Lett.

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The nuclear susceptibility and magnetization of a Van Vleck paramagnet PrCu 6 have been measured through the nuclear ordering transition. At zero magnetic field, the susceptibility shows a critical behavior at the transition temperature of 2 mK. This critical behavior shrinks and disappears as the applied magnetic field is increased. It is found that this behavior of the susceptibility is consistent with the electrical resistivity anomaly near the transition in its frequency and magnetic field dependence.The magnetization in magnetic fields shows a ferromagnetic increase at the transition, which coincides with the resistivity decrease in the ordered state. [S0031-9007(98)08321-5] PACS numbers: 75.40.Cx, 72.15.Eb, 75.30.Kz Nuclear magnetic moments are about 1/1000 the magnitude of the electronic moments so the electronic magnitude of the interaction between nuclear spins is roughly 6 orders less than that of electron spins. Hence the expected nuclear magnetic ordering temperatures for pure metals are low, ranging from mK to pK, and demagnetization of nuclear spins themselves is necessary to reach their nuclear ordering temperatures. In these cases, the nuclear spin system is not in equilibrium with the electron spin system which remains at a higher temperature. In the past two decades, nuclear magnetic ordering for pure metals has been studied progressively based on the concept of spin temperature [1], and some new spin structures, quite different from those of the electron spin systems, were found [2].There is another candidate for the nuclear magnetism of metals, the Van Vleck paramagnets, whose electronic ground state is a singlet in a crystal field. In Van Vleck paramagnets, nuclear spins couple strongly with electron spins through the hyperfine interaction [3] and order in the mK region due to an enhanced nuclear magnetic moment. Van Vleck paramagnets are, therefore, good candidates with which investigations of the nuclear magnetic ordering in thermal equilibrium to electron spin system can be carried out. Additionally the ordered state far below the transition temperature can be studied using a simple one stage copper nuclear demagnetization apparatus. The typical Van Vleck paramagnets are Pr compounds. We can study both nuclear ferromagnets and antiferromagnets in these Pr compounds by changing atomic species bound to Pr atoms and the anisotropy effect by selecting crystal structures. Moreover, we can investigate the nuclear ordering transition not only by measuring physical properties of nuclear spins (such as PrNi 5 , PrCu 6 , PrIn 3 , PrBe 13 ) [4-9] but also by examining electronic properties [10][11][12].In this Letter we have measured frequency-dependent nuclear susceptibility and static magnetization as a function of temperature and magnetic field through the nuclear ordering temperature and made a comparison with our former electrical resistivity measurement, where resistivity shows an anomalous behavior near the transition and decreases in the ordered state [11].We prepared a single crystal of P...

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confidence: 99%

Critical Behavior of Susceptibility at the Nuclear Ordering Transition inPrCu6

Akashi¹,

Kawabata²,

Matsubara³

et al. 1999

Phys. Rev. Lett.

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“…In addition, C ∼ 1/T α (α ∼ 1) behavior has been commonly seen in the T range close to the nuclear magnetic transition. For example, PrNi 5 , a prototypical system of the hyperfine-enhanced nuclear magnetism exhibits C ∼ 1/T α (α ∼ 1) behavior in the similar T range below 100 mK down to near the ordering temperature of 0.4 mK [27].…”

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Heavy-Fermion Superconductivity in the Quadrupole Ordered State ofPrV2Al20

et al. 2014

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PrV2Al20 is a rare example of a heavy fermion system based on strong hybridization between conduction electrons and nonmagnetic quadrupolar moments of the cubic Γ3 ground doublet. Here, we report that a high-quality single crystal of PrV2Al20 exhibits superconductivity at Tc = 50 mK in the antiferroquadrupole-ordered state under ambient pressure. The heavy fermion character of the superconductivity is evident from the specific heat jump of ∆C/T ∼ 0.3 J/mol K 2 and the effective mass m * /m0 ∼ 140 estimated from the temperature dependence of the upper critical field. Furthermore, the high-quality single crystals exhibit double transitions at TQ = 0.75 K and T * = 0.65 K associated with quadrupole and octapole degrees of freedom of the Γ3 doublet. In the ordered state, the specific heat C/T shows a T 3 dependence, indicating the gapless mode associated with the quadrupole and/or octapole order. The strong sensitivity to impurity of the superconductivity suggests unconventional character due to significant quadrupolar fluctuations.PACS numbers: 74.70. Tx, 75.25.Dk, 72.15.Qm 4f electron systems exhibit a large variety of nontrivial ground states by tuning the hybridization between localized 4f and conduction (c−) electrons. Especially, emergence of exotic superconductivity (SC) with a large effective mass from unconventional quantum criticality has attracted much attention [1][2][3][4][5]. While most of the examples have been reported at the border of magnetism [6,7], similarly exotic states of matter may be found in the vicinity of quantum phase transition associated with different degrees of freedom of f -electrons, such as electrical quadrupole (orbital) and valence. In particular, experimental exploration of the quadrupolar instability is important since few studies on the associated quantum criticality has been made to date.For the exploration, the simplest example could be found in materials that carry no magnetic but quadrupole moments. Such a nonmagnetic ground state is known as the Γ 3 doublet in the cubic crystalline electric field (CEF) of a f 2 configuration. Intensive studies have revealed various interesting states in the cubic Γ 3 doublet systems, in particular in Pr-based intermetallic compounds [8][9][10][11][12]. However, Pr-based cubic Γ 3 doublet systems usually have well-localized quadrupole moments, and thus until quite recently there have been no study on the quadrupolar instability by tuning the c-f hybridization.PrT r 2 Al 20 (T r = Ti, V) has been reported as a rare example of cubic Γ 3 -doublet based Kondo lattice systems where one may tune the hybridization strength between quadrupole moments and conduction electrons by chemical substitution and by pressure [13,14]. These materials have the nonmagnetic Γ 3 CEF ground state with the well separated excited state at ∆ CEF ∼ 60 K (Ti) and 40 K (V), as confirmed by various experiments [13,15,16], and * Electronic address: satoru@issp.u-tokyo.ac.jp exhibit the respective ferro-and antiferro-quadrupole ordering at T Q = 2.0 K (Ti) and 0.6 K (...

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“…Later Abragam et al 2 were able to observe ordering in the "truncated" nuclear spin systems of some insulators. Nuclear order has also been seen in Van Vleck systems like PrNi 5 , 3 and in solid 3 He, where spin exchange dominates. 4 However, the situation in the "brute force" studies on nuclear magnetism has so far remained obscure.…”

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confidence: 94%

Observation of a Magnetic Phase Transition in the Nuclear Spin System of Metallic Copper at Nanokelvin Temperatures

Huiku¹,

Loponen²

1982

Phys. Rev. Lett.

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A phase transition was observed in the nuclear spin system of metallic copper in external fields less than 0.22±0.02 mT and at entropies in the range of (0.4-0.6)R ln4; the transition temperature was estimated to be of the order of 100 nK. Indications of a second anomaly at 0.08 ± 0.01 mT were also seen. The transition is antiferromagnetic and of first order. It is accompanied with large overcooling of the paramagnetic phase, which explains the discrepancies in the previous results.PACS numbers: 75.30.Kz, 75.30.Cr, 75.50.Ee In this Letter we report the first unambiguous observation of spontaneous ordering of nuclear spins in metallic copper. Nuclear order was first sought in the pioneering experiments of Kurti et al. 1 Because of the limited precooling capacities then available, these early attempts were not successful. Later Abragam et al. 2 were able to observe ordering in the "truncated" nuclear spin systems of some insulators. Nuclear order has also been seen in Van Vleck systems like PrNi 5 , 3 and in solid 3 He, where spin exchange dominates. 4 However, the situation in the "brute force" studies on nuclear magnetism has so far remained obscure. The most extensive measurements have been carried out in our laboratory since 1974 with a two-stage nuclear demagnetization cryostat where the second copper stage also serves as the sample. 5 " 7 In the first set of experiments 5 the curve of entropy versus temperature was measured down to 0A5R ln4, corresponding to the extremely low temperature of about 50 nK. Yet no sign of a phase transition could be detected. In a later series of experiments, saturation of susceptibility was observed when the sample started warming up in zero field at low entropies. 6 These measurements suffered from a short spin-lattice relaxation time in zero field, r 1 (0), about 10 min in the first and 20 min in the second set of experiments. Later the saturation of susceptibility could not be reproduced, 7 but T 1 (0) was again less than 10 min.Failure to observe nuclear ordering, in these earlier experiments on copper, is in strong disagreement with theoretical predictions. 8 " 10 For the experimentally determined magnitude 6 of the Ruderman-Kittel indirect exchange interaction, together with the dipolar interaction, the predicted structure at T = 0 is k = (7r/a)(l 9 0, 0), exempli-fied by

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Nuclear Magnetic Ordering in PrNi5at 0.4 mK

Cited by 104 publications

References 16 publications

Critical Behavior of Susceptibility at the Nuclear Ordering Transition inPrCu6

Critical Behavior of Susceptibility at the Nuclear Ordering Transition inPrCu6

Heavy-Fermion Superconductivity in the Quadrupole Ordered State ofPrV2Al20

Observation of a Magnetic Phase Transition in the Nuclear Spin System of Metallic Copper at Nanokelvin Temperatures

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