Kiyohiro Sugiyama

Fermi Surface, Magnetic and Superconducting Properties of LaRhIn5 and CeTIn5 (T: Co, Rh and Ir)

We have studied Fermi surface properties of LaRhIn 5 and CeTIn 5 (T: Co, Rh and Ir) via the de Haas–van Alphen (dHvA) experiment. The Fermi surface of a non-4 f reference compound LaRhIn 5 is quasi...

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

We present recent advances in the magnetism and superconductivity of rare earth and uranium compounds. Heavy fermions are formed on the basis of the competition between the RKKY interaction and the Kondo effect in these compounds. The application of pressure to these compounds is useful to control the electronic states in the antiferromagnets CeRh 2 Si 2 and CeRhIn 5 , and the ferromagnet UGe 2 . The quadrupole interaction or the quadrupole Kondo effect is found to be responsible for heavy fermions in PrFe 4 P 12 . A rich variety of superconducting properties are demonstrated: superconductivity of CeCoIn 5 and CeRhIn 5 in the vicinity of a quantum critical point, coexistence of ferromagnetism and superconductivity in UGe 2 , and superconductivity based on the quadrupole fluctuations in PrOs 4 Sb 12 , together with the relation between the superconducting transition temperature and the quasi-two dimensionality of the electronic states.

Magnetic and Thermal Properties of CeIrIn5 and CeRhIn5

We studied the magnetic properties in a non-magnetic heavy-fermion compound CeIrIn 5 and an antiferromagnetic compound CeRhIn 5 with the tetragonal structure. High-field magnetization of CeIrIn 5 s...

High-Field Magnetization in PrCo2Si2 Single Crystats

Magnetic properties of PrCo 2 Si 2 single crystals have been studied by measurements of high-field magnetization, magnetic susceptibility and electrical resistivity. Anomalous behaviors in the resistivity appear at three successive magnetic phase transition temperatures of 9, 17 and 30K. The magnetic susceptibility is highly anisotropic and is analyzed using the single-ion Hamiltonian, including the crystal-field and molecular-field effects. The thermal variations of the susceptibilities can be well reproduced by the crystal-field parameters estimated from the point-charge model. Metamagnetic transitions with four steps are observable in the c -axis magnetization process up to 300 kOe. The magnetization process is discussed in terms of the incommensurate exchange field model in the Ising system proposed by Date.

Field-Induced Destruction of Heavy Fermion State in URu2Si2

High-field magnetization and magnetoresistance of URu 2 Si 2 single crystal are investigated up to 600 kOe. Three-step metamagnetic transitions are obtained with the transition fields of 358, 365 and 396 kOe at 1.3 K. The experimental results are explained quantitatively by introducing the model that the heavy Fermion state produced by the mixing of the f- and conduction electrons is destroyed by applying the field and that the exchange interactions between the recovered local f-electron magnetic moments on the uranium atom play an important role on the magnetic properties at high field. The frustration due to the exchange interactions induces the three-step metamagnetic transitions.

Field-induced metallic state in YbB12 under high magnetic field

High field magnetization and magnetoresistance of YbB 12 are investigated up to 550 kOe at low temperatures with special interest in the semiconductive band gap energy under the field. Very large negative magnetoresistance is found and the system is perfectly metallic around 500 kOe with anomalous increase in the magnetization. The experimental results are explained by introducing the model that the band gap produced by the mixing of the f- and conduction electrons is destroyed by applying the field and the released f-electron gives an anomalous magnetization. The g J -value is estimated as 1.9 for the f-level and this means that \(\varGamma_{8}\) may be most favourable for the responsible f-electron at the Fermi energy.

High Field Magnetization of Solid Oxygen

High field magnetization of solid oxygen is measured in the pulsed field up to 500 kOe. The spin flop field H c in the antiferromagnetic α-phase is investigated in detail and exchange and anisotropy fields are evaluated. The obtained data are compared with previously determined parameters and magnetic properties of three solid phases are satisfactorily explained. The α-phase is two-dimensional antiferromagnet with intrinsic Neel temperature of 30 K and the β-phase consists of the triangular spin short range order while the one-dimensional short range order exists in the A-15 type γ-phase. The corresponding exchange constants in these phases are determined by using the theory of low-dimensional magnetism and a systematic change is obtained throughout three phases.

Magnetic and Superconducting Properties of LaIrSi3and CeIrSi3with the Non-centrosymmetric Crystal Structure

Single crystals of LaIrSi 3 and CeIrSi 3 were grown by the Czochralski pulling method in a tetra-arc furnace and the magnetic and superconducting properties, together with superconductivity in CeIr 1- x Co x Si 3 , were clarified by measuring the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas–van Alphen (dHvA) effect. From the results of the dHvA experiment for LaIrSi 3 , the Fermi surface is found to split into two Fermi surfaces due to the spin–orbit interaction arising from the non-centrosymmetric crystal structure, which are separated by about 1000 K. Similar split Fermi surfaces are expected in the antiferromagnet CeIrSi 3 . The electronic state of CeIrSi 3 is tuned from the antiferromagnetic state to the superconducting state by applying pressure. The upper critical field H c2 (0) at a pressure of 2.65 GPa is found to be highly anisotropic: H c2 (0)=95 kOe for H ∥[110] and H c2 (0)≃300 kOe for H ∥[001], with the superconducting transition temperature T sc ≃...Single crystals of LaIrSi 3 and CeIrSi 3 were grown by the Czochralski pulling method in a tetra-arc furnace and the magnetic and superconducting properties, together with superconductivity in CeIr...

Upper critical field and resistivity of single-crystal EuBa2Cu

A wide-temperature-range profile of the H/sub c//sub 2/-T curve for the superconducting 1:2:3 compound is presented. The data were obtained from a EuBa/sub 2/Cu/sub 3/O/sub y/ single crystal under a pulsed magnetic field up to 50 T along the c axis. H/sub c//sub 2/ at 4.2 K is 27.5 +- 2.5 T for the onset of the resistivity. The residual resistivity is roughly estimated to be about 50 ..mu cap omega.. cm. The magnetoresistance is positive and the general features of the superconducting properties except T/sub c/ are well sketched by the Bardeen-Cooper-Schrieffer dirty-limit model. The anisotropies in H/sub c//sub 2/ and the resistivity are also discussed

High Field Magnetism of CuO

High field magnetization of CuO powder is measured in pulsed magnetic fields up to 360 kOe. The spin-flop field H c and the perpendicular magnetic susceptibility χ ⊥ are found to be 104 kOe and 2.7×10 -6 emu/g at 4.2 K, respectively. The exchange field H E of 6000±600 kOe and the anisotropy field H A of 0.9±0.1 kOe are estimated. CuO can substantially be regarded as a one-dimensional magnet with an intrachain exchange interaction J 0 / k of 400K and frustration effects are expected between the chains.