Tsuneaki Goto

Itinerant electron metamagnetism in YCo2

Abstract The magnetization measurement of an exchange-enhanced Pauli paramagnet YCo2 has been made at 10 K in pulsed ultra-high magnetic fields up to 94 T to examine the existence of itinerant electron metamagnetism. The field induced phase transition from a paramagnetic to a ferromagnetic state has been observed for the first time at about 70 T, indicating a clear evidence for the existence of metamagnetism.

Field-Induced Magnetic Transitions in the One-Dimensional Compound Ca3Co2O6.

Magnetization measurements on the one-dimensional oxide Ca 3 Co 2 O 6 having a triangular net of Co 2 O 6 chains have been carried out both in static and pulsed high magnetic fields. The M / H vs. T curve obeys the Curie-Weiss law at high temperatures. Below 25 K, however, M / H increases abruptly, and a plateau is observed at 1/3 of the full moment in the M - H curve, suggesting a ferrimagnetic state of the ferromagnetic chains due to the antiferromagnetic interchain interaction. At low H , this system is considered to be in a partially disordered antiferromagnetic state for 10 K< T <25 K and in a ferrimagnetic state below 10 K. The observed plateau in the M - H curve for T ≤5 K is broader than for 10 K≤ T ≤20 K, indicating spin freezing at lower temperatures. The results can be discussed in terms of the triangular Ising spin systems.

The anisotropic superconductivity of RBa2Cu3O7−x (R : Y, Gd and Ho) single crystals

Abstract Our study of high temperature superconductivity in RBa 2 Cu 3 O 7 − x (R:Y, Gd and Ho) using single crystal samples is reviewed with emphases on the anisotropic transport properties in the superconducting phase as well as the normal phase. Recent transport results obtained by use of a new technique for attaching a number of electrical leads on a small single crystal are also presented.

1/3 Magnetization plateau in SrCu2(BO3)2 : Stripe order of excited triplets

High-field magnetization measurements up to 57 T have been performed at 0.08 K in a single crystal of a two-dimensional spin-gap material SrCu 2 (BO 3 ) 2 . We successfully observed the predicted plateau at 1/3 of the total magnetization around 50 T, in which the magnetic superstructure is characterized by a novel stripe order of triplets. The 1/3 plateau is much wider than the previously observed 1/4 and 1/8 plateaux.

A laboratory instrument for generating magnetic fields over 200 T with single turn coils

An instrument has been developed that reliably generates pulsed magnetic fields in the range 150-250 T for experimental applications. A 100 kJ, 40 kV capacitor bank with 18 nH internal inductance and 2.9 m Omega internal resistance is discharged into single turn coils made of copper sheet of 3 mm thickness. 150 T are obtained in 10 mm diameter with a rise time (quarter period) of 2.5 mu s, 200 T are obtained in 6 mm ID within 2 mu s and 250 T in 4 mm ID within 1.8 mu s. Although the coils explode violently and generate a strong axial blast, there is no movement towards the magnetic field volume and even delicate samples can easily be protected to survive an experiment unharmed. This is demonstrated with two experiments: infra-red cyclotron resonance in a GaAs-AlGaAs superlattice and Faraday rotation in GaP.

High-Field Magnetization Processes of Double Spin Chain Systems KCuCl 3 and TlCuCl 3

High-field magnetization processes of S =1/2 double spin chain systems KCuCl 3 and TlCuCl 3 have been measured up to 39 T at 4.2 and 1.7 K for both systems and at 1.0 and 0.5 K for TlCuCl 3 using s...

Magnetization plateaus in NH4CuCl3

The magnetic susceptibility and high-field magnetization process of NH 4 CuCl 3 with double chains of CuCl 3 have been measured using single crystals. No anomaly indicative of the three-dimensional ordering is observed in susceptibility data above 1.7 K. It is found, by magnetization measurement down to 0.5 K, that in contrast to KCuCl 3 and TlCuCl 3 , NH 4 CuCl 3 has a gapless magnetic ground state at zero field. It is observed that the magnetization curve has two plateaus at one-quarter and three-quarters of the saturation magnetization, irrespective of the external field direction. The origin of the plateaus is attributed not to the magnetic anisotropy, but to the quantum effect. The relation between the plateaus and the period of the spin state is discussed in terms of a recent theory presented by Oshikawa et al . [Phys. Rev. Lett. 78 (1997) 1984].

Itinerant electron metamagnetism and peculiar magnetic properties observed in 3d and 5f intermetallics

A review is presented on the recent advances in theoretical and experimental studies of itinerant electron metamagnetism (IEM) found in 3d and 5f intermetallic compounds without magnetic rare-earth elements. These compounds exhibit various peculiar magnetic properties characteristic of IEM under high magnetic fields and high pressures. The observed IEM and peculiar properties are found to be qualitatively explained very well by theories of IEM based on the spin fluctuation model.

Magnetic properties and phase diagram of Ce(Ru1-xRhx)2Si2 (0≤x≤0.5)

Magnetic susceptibility, magnetization and specific heat measurements have been performed on single crystalline Ce(Ru 1- x Rh x ) 2 Si 2 in the Ru rich region(0≤ x 5 T). The AF ordering is destroyed above H C and the system further undergoes a metamagnetic transition at H M .

Upper Critical Field Measurements on a Single Crystal YBa2Cu3Ox up to 38 T

The anisotropic upper critical fields of a single crystal of orthorhombic YBa2Cu3Ox have been measured in pulsed high magnetic fields up to 38 T. The critical fields Bc2 defined by the onset of the resistance for parallel and perpendicular directions to the c-axis show a linear temperature dependence above 10 T with the slopes |dBc2///dT| = 1.1 T/K and |dBc2⊥/dT| = 3.9 T/K, whereas the Bc2 vs T curves show positive curvatures in the lower fields. At liquid nitrogen temperature, the zero resistance state cannot be destroyed by the field of 38 T and Bc2⊥ is estimated as 45 T.