Very low temperature properties of heavy fermion materials

Brison, Jean-Pascal; Keller, N.; Léjay, P.; Huxley, A.; Schmidt, L.B.; Buzdin, Alexandre I.; Bernhoeft, N.; Mineev, Iu. V.; Stepanov, A.; Flouquet, J.; Jaccard, D.; Julian, S. R.; Lonzarich, G. G.

doi:10.1016/0921-4526(94)91740-x

Cited by 50 publications

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“…To ensure good thermal contact at low temperature, each slice is ultrasonically bonded to a gold wire clamped to the silver plate. This method allows to reach low temperatures as shown previously by specific heat and thermal conductivity measurements [9].The µSR measurements were performed at the MuSR spectrometer [12] of the ISIS surface muon beam facility located at the Rutherford Appleton Laboratory (RAL, UK). The spectra were recorded with a 3 He-4 He dilution refrigerator (designed at the Commissariatà l'Energie Atomique, Saclay, France) for temperatures below 4.2 K and with a helium cryostat (a so called orange cryostat, Institut Laue Langevin, Grenoble, France) for temperatures up to 30 K. Some cross checked spectra were recorded down to 1.75 K with the orange cryostat.…”

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“…The as-grown crystals were annealed for several days at 1200 • C -1300 • C (see Ref. [9]), and then spark-cut or wire-sawed. The cut plates were annealed for an additional week at 950 • C, improving the sharpness of the resistivity transition (an example is presented at Fig.…”

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Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

et al. 1995

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We present muon spin relaxation measurements performed on crystals of the heavy fermion superconductor UPt3. In zero applied field, contrary to a previous report, we do not observe an increase of the internal magnetic field in the lower superconducting phase (the B phase). Our result gives an experimental upper bound of the magnetic field that could be associated with the superconducting state.PACS numbers : 74.70. Tx, 75.20.Hr, 76.75.+i The unconventional nature of superconductivity in the hexagonal heavy fermion superconductor UPt 3 is now well established [1]. This was first convincingly demonstrated by the occurence in zero magnetic field of two superconducting phase transitions at T C+ ≃ 0.50 K and T C * ≃ 0.45 K. Despite intense experimental and theoretical activities, the nature of superconductivity in UPt 3 is still unknown. Even the question of the symmetry of the superconducting order parameter is not resolved [2,3].Recently Luke et al. have reported zero field muon spin relaxation (µSR) measurements which show that the relaxation rate increases when crossing T C * from above [4,5]. This observation has been taken as a proof that the B phase (the low temperature superconducting phase below T C * ) breaks time reversal symmetry and is characterized by triplet Cooper pairs. This remarkable result has attracted much interest [6,7,2,8,3].The physical properties of heavy fermion metals are well known to be extremely dependent on the sample quality. High quality crystals are now available. These two facts have been our original motivation for performing new µSR measurements, the results of which are presented in this letter.The samples were prepared from two large single crystals of UPt 3 grown by the Czochralski method under ultrahigh vacuum from zone-refined depleted uranium. The as-grown crystals were annealed for several days at 1200 • C -1300 • C (see Ref.[9]), and then spark-cut or wire-sawed. The cut plates were annealed for an additional week at 950 • C, improving the sharpness of the resistivity transition (an example is presented at Fig. 1 of Ref. [10]). The resistivity of our samples, measured on long samples (8 mm length, 0.3 × 0.4 mm 2 cross section) obeys ρ(T ) = ρ(0) + AT 2 perfectly below 1.1 K, with ρ c (0) = 0.28 µΩcm, ρ a (0) = 0.51 µΩcm and A c = 0.90 µΩcmK −2 , A a = 1.46 µΩcmK −2 for current parallel to c and a. These low residual resistivities, which are comparable with recently published values [11], are a proof of the high quality of our samples.The µSR measurements were carried out on two samples which differ by the orientation of the crystal axes relative to the sample plane : either c or a * (≡ b) is perpendicular to it. Each sample is a disk of ∼ 18 mm diameter and ∼ 0.4 mm thickness, comprising of a mosaic of ∼ 10 aligned slices of the same single crystal carefully glued to a 5N silver plate (40 × 40 mm 2 ). To ensure good thermal contact at low temperature, each slice is ultrasonically bonded to a gold wire clamped to the silver plate. This method allows to reach low tempera...

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Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

et al. 1995

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“…The superconductivity is suppressed at a relatively low critical field of B c2 ϭ3 T for fields along the c axis. 29 The low-temperature specific heat for systems close to an antiferromagnetic instability can be described by the spinfluctuation model of Moriya and Takimoto. 30 The electronic specific heat related to the spin fluctuations depends on a characteristic temperature T 0 , a cutoff wave vector q c , and parameters y 0 and y 1 , which describe the reduced inverse staggered susceptibility y.…”

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Specific heat of heavy-fermionURu2Si2in high magnetic fields

et al. 1997

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We have performed specific-heat measurements on the heavy-fermion superconductor URu 2 Si 2 in magnetic fields up to 17.5 T. A sharp peak in the specific heat signals the antiferromagnetic transition at T N ϭ17.5 K, which shifts to lower temperatures in applied magnetic fields. In order to describe the specific heat below T N , we have used the characteristic features of the excitation spectrum measured by neutron scattering. The relative field dependence of the antiferromagnetic transition temperature T N and the energy gap ⌬ in the magnetic excitation spectrum can be described by a single scaling relation of the form ͓1Ϫ(B/B 0 ) 2 ͔. The scaling field of 48.5 T is close to the metamagnetic transition field B*ϭ40 T, where the heavy-fermion state is suppressed.

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“…A survey of publications indicates that the following media have been used in studies of URu 2 Si 2 : helium [7,8,25], 1:1 n-pentane/isoamyl alcohol [11,14,19,32,33], transformer oil/kerosene [12,34,35,36], 1:1 FC70/FC77 [15,16,17,20,21,22,25,26,27,34,35,36,37,38], 4:1 methanol/ethanol [39], argon [28], and Daphne oil [38]. In some reports, the pressure medium was not disclosed [9,10,13,18,23,29,31,40,30].…”

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Hydrostaticity and hidden order: effects of experimental conditions on the temperature–pressure phase diagram of URu₂Si₂

Butch

Jeffries

Zocco

et al. 2009

High Pressure Research

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The pressure-dependence of the hidden order phase transition of URu2Si2 is shown to depend sensitively upon the quality of hydrostatic pressure conditions during electrical resistivity measurements. Hysteresis in pressure is demonstrated for two choices of pressure medium: the commonly-used mixture of 1:1 Fluorinert FC70/FC77 and pure FC75. In contrast, no hysteresis is observed when the pressure medium is a 1:1 mixture of n-pentane/isoamyl alcohol, as it remains hydrostatic over the entire studied pressure range. Possible ramifications for the interpretation of the temperature-pressure phase diagram of URu2Si2 are discussed.

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Very low temperature properties of heavy fermion materials

Cited by 50 publications

References 15 publications

Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

Specific heat of heavy-fermionURu2Si2in high magnetic fields

Hydrostaticity and hidden order: effects of experimental conditions on the temperature–pressure phase diagram of URu₂Si₂

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Very low temperature properties of heavy fermion materials

Cited by 50 publications

References 15 publications

Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

Specific heat of heavy-fermionURu2Si2in high magnetic fields

Hydrostaticity and hidden order: effects of experimental conditions on the temperature–pressure phase diagram of URu2Si2

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Product

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Hydrostaticity and hidden order: effects of experimental conditions on the temperature–pressure phase diagram of URu₂Si₂