J. Flouquet

Low‐temperature properties of CeAl3

Specific heat measurements on CeAl3 are described and compared to thermal‐expansion results. At very low temperatures, the Gruneisen parameter reaches giant negative values. Comparisons are made with the properties of 3He and the unstable‐valent 4f compounds (YbCuAl, CeBe13, CeSn3, and CePd3). It is suggested that the magnetic anisotropy may play a major role.

Thermodynamic and transport properties of UPt3

In the normal phase of UPt3, the magnetoresistivity is large and positive with the striking feature of a quasi-independence of the temperature and magnetic field terms; the thermoelectric power has aT2 dependence and the susceptibility is almost constant up to 4 K. The superconducting transition is broadened and the specific heat jump is weak due to the strong anisotropy of its normal phase. FromTc to 146 mK (the lowest experimental temperature), a largeT2 contribution is observed in the specific heat, but the thermal conductivity has the same dependence only below 150 mK. These results are compared with the predictions given for polar odd-pairing superconductivity.

The normal phase of heavy fermion compounds

Abstract The properties of the normal phase of heavy Fermion compounds are reported. The data obtained on CeAl 3 show that two major scaling parameters appear T K and T ∗. They correspond to the competition between delocalization and interactions of the f electrons. Examples of long range ordering (magnetic in CeB 6 or superconducting in UBe 13 ) are chosen to define the main reservoirs and their changes through the transitions. A constant parameter “the renormalized Gruneisen-coefficient” seems to describe CeAl 3 as well as liquid 3 He.

Magnetic structure of the compound CeIn3

Abstract Neutron diffraction measurements on the CeIn3 compound show that the magnetic ordered phase is an antiferromagnetic one with a propagation vector ( 1 2 , 1 2 , 1 2 ) and a weak value of the magnetic moment 0.48±0.08 μB. Comparison are made with the CeAl2 and CeSn3 cases.

Magnetoresistivity experiments on CeAl3

Abstract Transverse magnetoresistivity (Δϱ ⊥ ) measurements on CeAl 3 are reported for 50 mK ⪕ T ⪕4.2 K and H ⪕60 kOe. Δϱ ⊥ changes sign at a temperature T x (∼1K) for H ≲25 kOe which represents the crossover from a single impurity behavior to a band phenomenon. T x decreases to ∼0.35 K for H ⪖45 kOe. The magnetoresistivity of CeAl 3 also shows anisotropic behavior.

Fermi liquid aspects in valence fluctuating systems

Abstract Low temperature properties of quasi-trivalent non-cubic compounds of cerium (CeAl 3 , CeCu 6 and CeRu 2 Si 2 ) are discussed with special emphasis on the role of the degeneracy of the ground state and of the symmetry of the lattice in the interactions between f electrons. In CeRu 2 Si 2 , an interesting new phenomenon, the occurrence of a polarized phase in a high magnetic field, is reported. The entrance in the intermediate valence regime and the possibility of couplings characteristic of a lattice are discussed.

Magnetic ordering in TmTe

Abstract Neutron diffraction experiments were performed on the divalent thulium compound TmTe. Magnetic structure determination leads to a type II antiferromagnet below the Neel temperature T N = .43 K. No crystal field excitations were observed.

The antiferromagnetic structure of tanol suberate

Abstract The (di-tetramethyl-2, 2, 6, 6-piperidinyl-4-oxyl 1) (C13H23O2NO)2 was considered for a long time to be the first purely organic ferromagnet with a moment carried by the 2p electrons of the NO groups. Neutron scattering experiments above and below the ordering temperature have permitted the determination of the magnetic structure, which in the absence of any applied magnetic field, is antiferromagnetic.

Transport and magnetic measurements on UPt3

Experiments on the normal phase of UPt3 show a large positive magnetoresistivity, almost temperature‐independent, linear in field, and a positive thermoelectric power which is not linear in temperature as T→0. The superconducting phase is characterized by a high thermal conductivity with a strong T2 term, by a coherence length smaller than the mean free path, and by lower and upper critical fields H(0)c1∼60 Oe and Hc2(0)∼26 kOe.

Transport properties of CeAl3 under pressure

Transport experiments on CeAl3 samples under quasihydrostatic pressure up to 1.63 GPa are reported. Magnetoresistivity measurements in magnetic fields up to 7.3 T from 40 mK to 4 K were performed. Resistivity and thermopower were measured from 1.5 to 300 K. Taking the low‐temperature resistivity as ρ=ρ0+AT2, A increases initially with pressure as expected from the zero pressure thermal dilatation. Above 0.2 GPa, both A and ρ0 decrease dramatically with pressure. It is, however, noteworthy that a T2 law of the resistivity can hardly be extracted from the data above 0.2 GPa. The positive low‐temperature magnetoresistivity also varies strongly with pressure. At 0.82 GPa the low field bump has disappeared and the magnetoresistivity is still positive up to 2.5 K. The thermopower shows an even more drastic pressure dependence. The negative bump around 3.5 K at zero pressure becomes positive above 0.3 GPa and a complex temperature dependence develops. The temperature variation cannot be scaled by a unique pressu...