Study on Unconventional Superconductivity and Magnetism in Heavy Fermion Superconductors by Means of Direct Measurements of Anisotropy

(I) Anisotropic Peak Effect in CeRu D22 D2Detailed magnetization measurements of CeRu D22 - D2单一crystals with different purity are performed at very low temperatures in order to clarifywhether their peak effects are due to the fled - frerrell - larkin - ovchinnikov (FFLO) transition. theonset field of the peak shifts to lower field side as the sample becomes impure. Regardless of thepurity the Ginzburg-Landau （G-L）κ D22 - D2 continues to increase on cooling from T - d - 2c - D2indicating little paramagnetic suppression of the superconductivity.这些影响disagree with thescenario of the FFLO transition (ii) Unconventional Superconductivity in Unconventional SuperconductivityD2Si D2Magnetization and specific heat measurements have been performed on ahigh-quality single crystal of heavy fermion superconductor Uru D22 D2Si D22 D2. Temperaturedependences of the G-L parameters κ D21 κ D2 and κ D22 κ D2together with those of upper critical field H - D2c2 - D2 and thermodynamic critical field - D2c - D2G-L parameters decrease both for H//c and for H//a - l parameters decrease both for H//c and for H//awith decreasing temperature from 1.1 K while in the temperature range between 1.1 K and T D2c D2G-L parameters slightly increase for H//a as temperature decreases. temperature dependenceD2 is similar to that of conventional superductors . These results suggest the presence ofparamagnetic suppression of the superconductivity at least in the low temperature region，consistent with the strong suppression of H - 2c2 - D2 at low temperatures.(iii) Anisotropy of theSuperconductivity in UPd - 22 D2Al - D23 - D2 was investigated by means of magnetizationmeasurements. The thermodynamic critical field H D2c was found to be 6x10 D12 Oe。

(I) Anisotropic Peak Effect in CeRuィイD22ィエD2Detailed magnetization measurements of CeRuィイD22ィエD2 single crystals with different purity are performed at very low temperatures in order to clarify whether their peak effects are due to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) transition. The onset field of the peak shifts to lower field side as the sample becomes impure. Regardless of the purity the Ginzburg-Landau (G-L) parameter, κィイD22ィエD2 continues to increase on cooling from TィイD2cィエD2, indicating little paramagnetic suppression of the superconductivity. These results disagree with the scenario of the FFLO transition.(ii) Unconventional Superconductivity in UruィイD22ィエD2SiィイD22ィエD2Magnetization and specific heat measurements have been performed on a high-quality single crystal of heavy fermion superconductor UruィイD22ィエD2SiィイD22ィエD2. Temperature dependences of the G-L parameters κィイD21ィエD2 and κィイD22ィエD2, together with those of upper critical field HィイD2c2ィエD2 and thermodynamic critical field HィイD2cィエD2, were obtained from the above measurements. The G-L parameters decrease both for H//c and for H//a with decreasing temperature from 1.1 K while in the temperature range between 1.1 K and TィイD2cィエD2 the G-L parameters slightly increase for H//a as temperature decreases. Temperature dependence of HィイD2cィエD2 is similar to that of conventional superconductors. These results suggest the presence of the paramagnetic suppression of the superconductivity at least in the low temperature region, consistent with the strong suppression of HィイD2c2ィエD2 at low temperatures.(iii) Anisotropy of the Superconductivity in UPdィイD22ィエD2AlィイD23ィエD2 was investigated by means of magnetization measurements. The thermodynamic critical field HィイD2cィエD2 was found to be 6x10ィイD12ィエD1 Oe.