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

(I)Anisotropic Peak Effect in CeRu I D 22 ii D 2 Detailed magnetization measurements of CeRu I D 22 ii 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-ii D22--D2 continues to increase on cooling from T-I D2c-i D2，indicating little paramagnetic suppression of the superconductivity。These results disagree with the scenario of the FFLO transition.(Ii)Unconventional Superconductivity in Uru I D22文件D2Si文件D22文件D2 Magnetization and specific heat measurements have been performed on a high-quality single crystal of heavy fermion superconductor Uru文件D22文件D2.Temperature dependences of the G-L parametersκD 21个D 2 andκD 22个D 2，together with those of upper critical field H I D2c2个D2 and thermodynamic critical field H个D 2个D 2，were obtained from the above measurements。The G-L parameters decrease both for H//c and for H//a with decreasing temperature from 1.1K while in the temperature range between1.1K and T I D2c项目D2the G-L parameters slightly increase for H//a as temperature decreases.Temperature dependence of H I D2cⅡD2is 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 I D2c2西耶D2 at low temperatures.(Iii)Anisotropy of the Superconductivity in UPd I D22西耶D2Al I D23西耶D2was investigated by means of magnetization measurements。The thermodynamic critical field H I D 2 c D 2 was found to be 6 x 10 I D 12 I D 1 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.