T. Graf

Response of CeRh2Si2 to pressure

Abstract Under atmospheric pressure, CeRh2Si2 orders antiferromagnetically at TN = 35 K, with magnetic entropy S = Rln2 associated with the ordered groundstate. Application of modest pressure (≈ 9 kbar) to CeRh2Si2 suppresses TN to near zero Kelvin, increases its Sommerfeld coefficient of specific heat by nearly a factor of 3.5 and induces some form of superconductivity below 400 mK which is depressed by a magnetic field at a rate of − 80 mK/kG.

Magnetism in CeRu2Ge2 and CeRh2Ge2 and its pressure dependence

Abstract We have studied magnetism in CeRu 2 Ge 2 and CeRh 2 Ge 2 through specific heat in zero and applied magnetic fields, DC magnetization, thermal expansion and electrical resistance measurements at pressures to 21 kbar. Both compounds have two magnetic transitions; although we argue that the higher one in CeRu 2 Ge 2 is due to residual stress in the polycrystalline sample. The overall systematics are consistent with those found at ambient pressure in pseudoternaries formed with Si substitution for Ge.

High field magnetotransport and specific heat in YbAgCu4

The electrical resistivity (ρ{variant}) and magnetoresistance of polycrystalline YbAgCu4 have been measured at temperatures between 25 mK and 300 K, and at magnetic fields (B) up to 18 T. The magnetoresistance (ρ{variant}(B) - ρ{variant}(0))/ρ{variant}(0)) is positive at all temperatures below 200 K and reaches its maximum of 60% at 18 T and 25 mK. The field- and temperature-dependent resistivity does not scale in a simple way. The opposite sign of the magnetoresistance at ambient and high pressure can be explained qualitatively by crystal-field effects lifting the degeneracy of the J = 7 2 groundstate. The linear coefficient of the specific heat (γ) measured at fields up to 10 T shows a quadratic field dependence. We did not find a linear relation between γ2 and A, the T2-coefficient of the temperature-dependent resistivity, with the applied magnetic field as the implicit parameter.

Effect of pressure of the magnetic transitions in CeRh2Ge2 and CeRu2Ge2

We have studied the effect of pressure on the magnetic transition in CeRh 2 Ge 2 and CeRu 2 Ge 2 by electrical resistance measurements in the temperature range between 1.2 K and 300 K. Both samples show two magnetic transitions below 30 K. In CeRh 2 Ge 2 , the magnetic transition temperatures increase with increasing pressure. In the case of CeRu 2 Ge 2 , the upper magnetic transition temperature increases with pressure, whereas the lower one decreases with increasing pressure

Effect of high pressure and magnetic field on the electrical resistivity of YbAgCu4

Abstract The electrical resistivity of YbAgCu4 has been measured at pressures up to 100 kbar and at temperatures between 1 and 300 K. With increasing pressure, the resistivity maximum shifts to lower temperatures and the coherent regime disappears above about 60 kbar. At the highest pressures, a field of 8 T produces a large negative magnetoresistance, roughly equivalent to a negative pressure of 30 kbar. The behavior is consistent with a pressure-induced decrease in the Kondo temperature.

High field magnetoresistance of La1.99Sr0.01CuO4+δ

Abstract The in-plane resistance of a La 1.99 Sr 0.01 CuO 4 single crystal has been measured as a function of temperature (4K 2+ spin component.

Magnetic field dependence of Tc of EuB6 (abstract)

We report measurements of resistivity and transverse magnetoresistance (B⊥I) on a single crystalline sample of EuB6 in magnetic fields to 18 T in a temperature range from 4 to 100 K. The ferromagnetic transition (Tc) determined by resistivity versus temperature at constant field varies from 10 to 25 K at zero and 4 T, respectively. The transition is completely suppressed at 8 T. A very large and negative tranverse magnetoresistance is observed in the entire temperature range investigated: −5% at 4 K and −20% at 100 K at 18 T. Finally, the effect of high applied magnetic field on the transport properties is investigated in the temperature range below Tc.