Michiro Suzuki

Anomalous Susceptibility of UPd2Al3 near the Upper Critical Field.

The ac susceptibility of the heavy fermion superconductor UPd 2 Al 3 has been measured. The peak of the susceptibility has been observed in the vicinity of the upper critical field. This anomaly is explained by the flux pinning rather than by the Fulde-Ferrell state.

de Haas-van Alphen Effect and Fermi Surface of USb

The de Haas-van Alphen effect has been measured in a semimetallic compound USb from at temperatures down to 45 mK and in fields up to 13.5 T. The observed three kinds of signal branches indicate that there exist two sets of ellipsoidal Fermi surfaces with different sizes and one spherical Fermi surface. The measured effective mass ratios m * / m 0 are in the range between 0.9 and 2.7.

dHvA measurement in a semimetallic compound U3P4

Abstract We report de Haas-van Alphen (dHvA) measurements with a 3He−4He dilution refrigerator in U3P4. The uranium compound U3P4 crystallizes in the BCC Th3P4-type structure with a space group Td6 (I 4 3d). This compound is ferromagnetic below 137 K with a complex triaxial magnetic structure. Our measurements reveal new sheets of the Fermi surface which have heavy cyclotron effective masses and suggest open orbitsin the (111) plane. We have clarified that the Fermi surfaces of U3P4 are not so simple as those expected before.

De Haas-van Alphen effect in CoS2

Abstract We present the first measurement of the de Haas-van Alphen (dHvA) effect in CoS 2 at temperatures down to 50 mK and in fields up to 13.5 T. It was found that mainly five kinds of branches exist and the largest effective mass is about 5.0 m 0 . The experimental result agree with the result of the band calculation at high dHvA frequencies, except at low frequencies.

Anisotropy of Current‐pumped Nuclear Spin Polarization in the ν = 2/3 Quantum Hall State

We investigate the anisotropy of the current‐pumped nuclear spin polarization by changing an angle φ between the current I and the in‐plane magnetic field B∥. The nuclear spin polarization develops at the spin transition point of the quantum Hall state at the Landau level filling factor ν = 2/3. When large I is driven, the nuclear spin polarization appears independently of φ. However, as I is decreased, the polarization disappears when B∥ is parallel to I, while it remains when B∥ is perpendicular to I. The anisotropy indicates the difference of the nuclear spin pumping rate about the direction of B∥.

Anisotropic Behavior of Hysteretic Transport Phenomena in the ν = 2/3 Quantum Hall State in the Tilted Magnetic Field

We study an anisotropic transport around the spin transition point at the Landau‐level filling factor ν = 2/3 in tilted magnetic fields. When the direction of the in‐plane component of the magnetic field (B∥) is normal to the current I, a strong hysteretic transport due to the domain structure of different spin configurations occurs. As the angle φ between B∥ and I is decreased, the hysteresis becomes small, and almost disappears when the direction of B∥ is along I. We suggest that domain walls are aligned parallel to B∥, and the number of electrons scattered by domain walls increases with φ.

ANISOTROPIC TRANSPORT ON THE ν=1 BILAYER QUANTUM HALL SYSTEM UNDER TILTED MAGNETIC FIELD

We measured an anisotropic magnetotransport that depends on directions of an in-plane field in a bilayer quantum Hall system. We found that the longitudinal resistance near the bilayer ν=1 quantum Hall state strongly varies when we changed an relative angle between the current and the in-plane field. It is a phenomenon peculiar to the bilayer ν=1 quantum Hall state, because this phenomenon does not appear in a monolayer system.

Anomalous flux pinning of UPd2Al3

The ac magnetic susceptibility of UPd2Al3 in the superconducting state has been measured to test of the existence of the Fulde, Ferrell, Larkin and Ovchinnikov (FFLO) state. A dip in the susceptibility has been observed in the vicinity of the upper critical field and the temperature range from zero to Tc. This dip is very sensitive to the amplitude of the ac magnetic field. The anomaly is explained by the increase of the flux pinning effect. Recent theories suggest that the pinning force becomes stronger in the FFLO state, and the existence of the nonuniform state due to the order parameter mixing in a d-wave superconductor is possible near Tc.

Anisotropic Magnetotransport near the Bilayer ν = 2/3 Quantum Hall State

We study a magnetotransport anisotropy of a bilayer electron system at the Landau level filling factor ν = 2/3 under tilted magnetic fields. When the direction of the applied in‐plane component of magnetic fields with respect to the current is altered, an anisotropy appears only when the interlayer tunneling is allowed. Therefore the phenomenon suggests that the interlayer tunneling process is affected by the direction of the in‐plane field.

In‐plane field induced anisotropy of the longitudinal resistance in a bilayer quantum Hall system

We examine an anisotropic transport in a bilayer system around the quantum Hall state at the total Landau level filling factor v = 1. We find that the anisotropy becomes remarkable at the phase transition point between the commensurate and incommensurate states. This result suggests that a unidirectional state appears around the transition.