L. Puech

Metamagnetic CeRu2Si2: New perspectives for heavy-fermion studies in high fields

Abstract Interesting magnetic effects have recently been reported to occur in the normal phase of heavy-fermion systems. Among them are the metamagnetic properties of UPt 3 and CeRu 2 Si 2 ( H M = 20 and 8 T). High-pressure magnetization and magnetoresistance, as well as magnetostriction measurements have been performed on CeRu 2 Si 2 . The magnetostriction data imply a remarkable scaling behavior for the magnetization as a function of P and thus a relation between H M and the characteristic Fermi-liquid energy k B T ∗ . The magnetoresistance suggests that the field enhancement of the effective mass derived from the specific-heat γ( H ) leads to the observed transition at H M for a critical value of m ∗ which is pressure independent.

Low-temperature properties of the heavy-fermion compound CeRu2Si2 at the metamagnetic transition

Magnetization measurements performed below 1 K on a single-crystalline sample of the heavy fermion compound CeRu2Si2 are reported. The field variation of the linear term of the specific heat γ derived from these data (via a Maxwell relation) exhibits a large peak at the metamagnetic-like transition at B* (=7.7 atT → 0). Thermal-expansion measurements, show a drastic drop of the temperature where a Fermi liquid behavior is reached whenB →B*. Similar experiments performed on a single-crystalline Ce0.95La0.05Ru2Si2 sample show a broadening of all the anomalies atB* and a reduction of their intensities. These results strongly suggest that pure CeRu2Si2 approaches a magnetic instability atB* forT → 0.

High-field magnetostriction in the pseudo-metamagnetic heavy-fermion system CeRu2Si2

Low-temperature magnetostriction experiments have been performed on CeRu2Si2 single crystals in magnetic fields up to 15T. WhenH is applied parallel to the tetragonalc-axis, a very large expansion is observed in all lattice directions. A pronounced anomaly occurs at a field close to the “metamagnetic” threshold. The results are discussed with use of thermodynamic relations and support a very simple scaling behavior for the pressure dependence of the magnetization.

Mobility of the3He solid-liquid interface: Experiment and theory

Two experiments are presented that show that the growth resistance of3He crystals is smaller than expected. In order to explain this result the growth resistance is calculated in two different ways, showing that the experimental results are best understood if the liquid quasiparticles interact with the crystal lattice instead of the interface.

Evidence for a disorder-driven phase transition in the condensation of 4He in aerogels

We report on thermodynamic and optical measurements of the condensation process of

Polarized 3He: A New Phase?

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Sound Velocity in Highly Polarized 3 He

He in three silica aerogels of different microstructures. For the two base-catalysed aerogels, the temperature dependence of the shape of adsorption isotherms and of the morphology of the condensation process show evidence of a disorder driven transition, in agreement with recent theoretical predictions. This transition is not observed for a neutral-catalysed aerogel, which we interpret as due to a larger disorder in this case.

Thermal expansion at the metamagnetic transition in single‐crystalline heavy‐fermion (Ce,La)Ru2Si2

Using the results of a previous analysis, we demonstrate a recently advanced hypothesis. Under some conditions which we state explicitly, during melting of polarized 3He, the mean measured magnetization is also that of the liquid at the interface. It allows us to use the data of a previous experiment to obtain the susceptibility of the liquid dm/dH vs. the field. The results suggest the existence of a metamagnetic transition, at round 40 Tesla.

Magnetovolume study of the metamagnetic transition of CeRu2Si2 below 1 K

By rapid complete melting of polarized solid, we have obtained liquid 3He in an effective magnetic field of 130 T. The sound velocity has been measured at various pressures in this highly polarized liquid. The main result is a linear dependence of this velocity vs. the square of the polarization up to 30%. We deduce an upper limit for a deviation from this law.

Magnetostriction of Heavy-Fermion UPt3 in Magnetic Fields up to 24 Tesla

We present measurements of the volume expansion (αv) in magnetic fields up to 8.5 T and in the temperature range 1.3 K<T<20 K on the heavy‐fermion compounds Ce1−xLaxRu2Si2 (x=0 and 0.05). In reduced scales the two compounds present the same low temperature Gruneisen coefficients. Emphasis is given on the strong field dependence of the low temperature extremum of αv. The validity of scaling law with pressure is verified. The interest to use a magnetic field to approach a magnetic instability is strongly underlined.