Isamu Ukon

Magnetic and electrical properties of U-Ge intermetallic compounds

We have clarified the magnetic and electrical properties of U 7 Ge, U 5 Ge 3 , U 3 Ge 4 and UGe 2 , measuring the electrical resistivity, thermoelectric power, Hall coefficient, magnetic susceptibility, magnetization and specific heat. U 7 Ge and U 5 Ge 3 , which are Pauli paramagnetic compounds, become superconductive below 1.40 K and 0.99 K, respectively. The latter compounds U 3 Ge 4 and UGe 2 indicate ferromagnetism. Anisotropic properties of UGe 2 are well reflected in the electrical resistivity, magnetic susceptibility and magnetization.

Anomalous Hall Coefficient in the f Electron system– Ce Compounds

We report the temperature dependence of Hall coefficient of RCu 6 (R: La, Ce, Pr, Nd and Sm), Ce x La 1- x Cu 6 and typical Ce compounds (CeRu 2 , CeSn 3 , CePd 3 , CeCu 2 Si 2 , CeAl 3 , CeInCu 2 , CeAl 2 , CeIn 3 and CeB 6 ) in the temperature range of 0.7 K to room temperature. The f electrons of these substances show a wide variety of behavior including Pauli itinerance, mixed valence, heavy fermion and localized moment system. These characteristics are well reflected in the Hall coefficient. The Hall coefficient of Ce x La 1- x Cu 6 at higher temperatures than 30 K is well fitted by the recent skew scattering Hall effect theory.

Metamagnetic behavior in the Kondo lattice substance CeCu2

Abstract We report competition between the negative magnetoresistance due to the Kondo effect and the positive magnetoresistance due to the cyclotron motion of the carriers in CeCu2.

Normal and superconducting properties of the magnetic superconductor URu2Si2

Disappearance of the paramagnetic Fermi surface in URu2Si2 due to the formation of spin density waves is well reflected in the electrical resistivity, Hall coefficient, thermoelectric power and magnetic susceptibility. Pressure dependences of the Neel temperature, superconducting transition temperature and superconducting upper critical field are also investigated.

Superconductivity in U5Ge3

We have found superconductivity in U 5 Ge 3 at 0.99 K. The slope of the superconductive upper critical field at T c , -d H c2 /d T is 5.5 kOe/K, and H c2 (0) is estimated to be 3.8 kOe.

Heavy cyclotron mass in ferromagnetic substance UGe2

Abstract We have measured transverse magnetoresistance and the de Haas-van Alphen effect in an anisotropic ferromagnetic substance UGe 2 . Fermi surfaces consist of multiple-connected large cylindrical sheets and ellipsoidal closed ones. Carriers possess large cyclotron effective masses, ranging from 2 to 2 m 0 .

Superconductivity in U5Ge3 and U7Ge

Abstract We have found superconductivity in U5Ge3 and U7Ge at 0.99 and 1.40 K, respectively. The slope of the superconductive upper critical field at Tc, −dHc2/dT is 5.5 kOe/K for U5Ge3 and 2.1 kOe/K for U7Ge, and Hc2(0) is estimated to be 3.80 kOe for U5Ge3 and 1.99 kOe for U7Ge.

Electrical and magnetic properties of U-X (X = Ru, Rh and Ir) intermetallic compounds

We have studied the electrical and magnetic properties of U–X (X=Ru, Rh and Ir) intermetallic compounds by measuring the electrical resistivity, Hall coefficient, thermoelectric power, specific heat, magnetic susceptibility and magnetization. We have found a variety of behaviors of antiferromagnetism, ferromagnetism and superconductivity in these compounds.