F. Lapierre

The heavy fermion compound CeRu2Si2: Magnetic instability, lattice quasicollapse and metamagnetism

Abstract The physical properties of the heavy fermion compound CeRu 2 Si 2 are reviewed. Since this compound is close to a magnetic instability, special attention is paid to its magnetization in which a metamagnetic-like transition occurs at a field H M of 7.7 T and to the strong coupling between this effect and the volume, leading to a quasi-collapse of the lattice. It is shown that the value of the differential susceptibility at H M reaches an intrinsic finite limit at very low temperature. Different theoretical models are discussed.

Magnetization of (Ce,La)Ru2Si2 and (Ce,Y)Ru2Si2 single crystals

Abstract Magnetization measurements performed on single crystals of Ce 1− x La x Ru 2 Si 2 and Ce 1− y Y y Ru 2 Si 2 with with H parallel to the tetragonal c -axis are reported. The variations of the metamagnetic transition fields observed in the paramagnetic state and in the antiferromagnetically ordered alloys follow those of the Kondo temperature.

Electrical resistivity of (Ce,La)Ru2Si2 alloys

Abstract Electrical resistivity ϱ( T ) measurements performed on tetragonal Ce 1− x La x Ru 2 Si 2 single crystals down to 20 mK are reported. A Kondo behaviour with a logarithmic slope linear with x is observed for x ≥ 0.3. The variations of ϱ near the antiferromagnetic transition are discussed.

Magnetoresistance of (Ce,La)Ru2Si2 alloys

Abstract Magnetoresistance measurements on Ce1−xLaxRu2Si2 single crystals are reported. For x = 0.05 a maximum of ϱ is observed at the metamagnetic-like transition field as in CeRu2Si2. In the AF-ordered alloys, ϱ(H) is always negative above TN, while below TN it drops at the magnetic transitions and reproduces their hysteresis effects.

Resistivity anisotropy in CeRu2Si2

Abstract Measurements of the electrical resistivity with the current parallel ( ϱ ‖ ) or perpendicular ( ϱ ⊥ ) to the c -axis of CeRu 2 Si 2 and LaRu 2 Si 2 single crystals are reported. The magnetic resistivity anisotropy ( ϱ m‖ / ϱ m⊥ ), deduced after substraction of ϱ(LaRu 2 Si 2 ), goes to a maximum near 15 K. The results are compared to those reported for other intermetallic compounds.

Concentration dependence of the pseudometamagnetic field in heavy fermion Ce1−xYxRu2Si2

Abstract Magnetization measurements performed on Ce1−xYxRu2 single crystals at low temperature for the magnetic field parallel to the easy magnetization axis (c-axis of the tetragonal structure) are reported. They show an increase of the metamagnetic-like field HM, from about 8 T for x = 0 to a value of 20 T for x = 0.1. The Gruneisen parameter derived from the increase of HM is compared to those already derived from other experiments, especially from the variation of TK deduced from specific heat measurements.

Influence of Y and La alloying on the anomalous hall effect of CeRu2Si2

Abstract Hall effect experiments on Ce1−yYyRu2Si2 (y ≤ 0.2) and Ce1−xLaxRu2Si2 (0.9 ≤ x ≤ 0) alloys are reported. They show a shift of the maximum of RH (≈ 18 K for x = y = 0) to higher temperatures for Y substitution and to lower temperatures for La substitution consistent with the variation of the Kondo temperature deduced from specific heat experiments. The high temperature variations of RH are compared to theoretical models.

Magnetoresistivity below TN in CeMo6S8

Abstract The T ⩾1.15xa0K resistivity of two CeMo 6 S 8 Chevrel single crystals is reported. It shows the occurrence of (presumably) antiferromagnetic (AF) order at T N ≈2.1 and 2.55xa0K, respectively, in agreement with previous results. The magnetoresistance, measured on sample 1 shows a drop below T N for a field B c ≈1.25xa0T at 1.6xa0K. This behavior suggests the crossing from an AF state to a polarized state. It is discussed in connection with other results reported for this compound.