Sadayoshi Koiwai

The pressure dependence of magnetization of layered perovskite oxides with 4d-electron metal

Abstract Magnetization measurements for the spin-triplet superconductor Sr 2 RuO 4 under uniaxial pressure and for its relative compound Sr 3 Ru 2 O 7 under both hydrostatic and uniaxial pressures have been performed from 2 to 300 K. Those samples are single crystals grown by a floating-zone method. Uniaxial pressure normal to the two-dimensional RuO 2 plane up to 0.4 GPa has not shown a dramatic effect on the magnetism of single crystalline Sr 2 RuO 4 . Magnetization of single crystalline Sr 3 Ru 2 O 7 under hydrostatic pressure up to 1.4 GPa has indicated that there is no ferromagnetic ordering around 70 K which was observed in our previous work. To clarify these different results, magnetization measurements under uniaxial pressure normal to the RuO 2 plane for single crystals of Sr 3 Ru 2 O 7 is also provided. The results imply that the uniaxial component is essential for the appearance of ferromagnetism.

μSR study of magnetism of CeRh2Si2 under a high pressure

Abstract CeRh2Si2 shows two successive antiferromagnetic phase transitions at ambient pressure (T N 1 =36 K and T N 2 =27 K ). Application of pressure suppresses TN1 to 0 K at P c ∼1 GPa . We study the magnetism of the single-crystalline sample of CeRh2Si2 by muon spin rotation/relaxation (μSR) method up to 0.45 GPa . Below TN2, we observed both the spontaneous muon spin precession and the fast muon spin relaxation under zero magnetic field. Although the transition temperature decreases with increasing the pressure, the precession frequency, which is proportional to the saturated sublattice magnetic moment, is nearly independent of the pressure.

Magnetic properties of Ce3PbC

Abstract Ternary compound Ce3PbC has a simple face-centered cubic CaTiO3-type structure. We found that Ce3PbC undergoes a transition to an antiferromagnetic state at T N =8.4 K and shows an another transition at T t =5.8 K . Magnetization process exhibits multi-step metamagnetic transitions at T=1.5 K . The observation of inelastic neutron experiments suggest that the crystalline electric field (CEF) ground state can be consider to be a doublet. This results imply that the Ce sites are influenced by tetragonal CEF interaction, even though the crystal structure is cubic. We expect that such CEF configuration plays an important role in the behavior of multi-step metamagnetic transitions.

The H–T phase diagrams of CeGa under high pressure for H||a-axis and H||c-axis

Abstract The magnetic susceptibility and the electrical resistivity of single crystal CeGa are measured in magnetic fields up to 9 T and at pressures up to 7.0 kbar . Antiferromagnetic transition temperature T N =5.8 K decreases and fades out above 5 T with increasing magnetic fields along the c -axis at various pressures up to 4.9 kbar . On the other hand, the T N decreases slightly with increasing magnetic fields applied along the a -axis up to 9 T and at various pressures up to 7.0 kbar . These results can be explained on the basis of magnetocrystalline anisotropy effects.

Field-induced non-Fermi liquid behavior of CeGa single crystal

Abstract We measured the specific heat capacity of single-crystal CeGa in the temperature range 2.0 K ⩽T⩽300 K and under magnetic fields up to H=9 T . A λ-type anomaly is observed at T N =6 K . The electronic specific heat coefficient γ was determined to be 139 mJ / mol K 2 . With increasing magnetic field, TN decreases and vanishes at H∼7 T , completely. When TN is just suppressed, i.e., T N →0 K , C/T shows indication of a − log T dependence.

High-field magnetization of RCo2Si2 (R = Gd, Tb)

Abstract High-field magnetization and magnetic susceptibility have been measured on RCo 2 Si 2 (R=Gd, Td) single crystals with the tetragonal ThCr 2 Si 2 -type of structure. Typical features for a simple antiferromagnetic structure with small and large magnetic anisotropy are observed on the Gd- and Tb-compounds, respectively; a linear magnetization curve with a small spin–flop transition in the Gd-compound and a two-step metamagnetic process in the Tb-compound are seen.