Showing papers by "Tatsuo C. Kobayashi published in 2006"
99 citations
TL;DR: In this article, a high-pressure AC-susceptibility measurement has been carried out in UIr. The Meissner effect is observed successfully in the pressure range of 2.63 −2.74 GPa.
Abstract: High-pressure AC-susceptibility measurement has been carried out in UIr. Three series of peaks corresponding to the successive ferromagnetic transitions indicate the existence of three ferromagnetic phases FM1-3. The phase boundary between FM2 and FM3 was not realized in the resistivity measurement. The Meissner effect is observed successfully in the pressure range of 2.63–2.74 GPa where the peak of AC-susceptibility survives. This result indicates that the superconducting phase is embedded in the FM3 phase with the ordered moment less than 0.05 μ B /U and adjoins the quantum critical point.
26 citations
TL;DR: The antiferromagnet CeNiGe 3 exhibits superconductivity under pressure as mentioned in this paper, and the Neel temperature initially increases with increasing pressure up to 3 GPa and then becomes zero at a critical pressure.
Abstract: The antiferromagnet CeNiGe 3 exhibits superconductivity under pressure. The Neel temperature initially increases with increasing pressure up to 3 GPa and then becomes zero at a critical pressure ( ...
25 citations
TL;DR: Specific-heat experiments on single crystals of the S = 1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C9H24N4)(NO2)ClO2 (NTENP) have been performed, providing conclusive evidence for a Tomonaga-Luttinger liquid.
Abstract: Specific-heat experiments on single crystals of the S = 1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C9H24N4)(NO2)ClO2 (NTENP) have been performed in magnetic fields applied both parallel and perpendicular to the spin chains. We have found for the parallel field configuration that the magnetic specific heat (C(mag)) is proportional to temperature (T) above a critical field H(c), at which the energy gap vanishes, in a temperature region above that of the long-range ordered state. The ratio C(mag)/T increases as the magnetic field approaches H(c) from above. The data are in good quantitative agreement with the prediction of the c= 1 conformal field theory in conjunction with the velocity of the excitations calculated by a numerical diagonalization, providing conclusive evidence for a Tomonaga-Luttinger liquid.
19 citations
TL;DR: In this paper, the physical properties of a pressure-induced insulating phase in PrFe 4 P 12 via Hall effect, 31 P-NMR and magnetization measurements under quasi-hydrostatic pressure were studied.
Abstract: We have studied the physical properties of a pressure-induced insulating phase in PrFe 4 P 12 via Hall effect, 31 P-NMR and magnetization measurements under quasi-hydrostatic pressure. In the Hall ...
9 citations
TL;DR: In this paper, the authors measured the anisotropy in the electrical resistivity of CexLa1−xAgSb2 to study the p-f mixing effect, and small humps were observed in the temperature dependence of the resistivity.
Abstract: CeAgSb2 crystallizes in the tetragonal ZrCuSi2 type structure (P4/nmm), which consists of Sb–Ce, Sb–Ag–Ce, Sb–Sb layers. It shows the peculiar anisotropic ferromagnetic ordering below 9.7 K with a small ordered moment of 0.33 μB. Its residual resistivity steeply increases above p c ≅ 3.3 GPa where the magnetic order disappears. It is expected that the p–f mixing on the peculiar hollow square pillar-like Fermi surface plays an important role in CeAgSb2, while similar Fermi surfaces were not observed in LaAgSb 2 . We have measured the anisotropy in the electrical resistivity of CexLa1−xAgSb2 to study the p–f mixing effect. Small humps were observed in the temperature dependence of the resistivity in CexLa1−xAgSb2. We expected them the CDW transition. The CDW state coexisted with the ferromagnetic state around x = 0.2 .
6 citations
TL;DR: In this article, the authors present evidence for unconventional superconducting fluctuations in a heavy-fermion compound CeNi2Ge2, which indicates the development of magnetic correlations and the formation of a Fermi-liquid state at temperatures lower than TFL ¼ 0:4 K, where 1=T1T is constant.
Abstract: We present evidence for unconventional superconducting fluctuations in a heavy-fermion compound CeNi2Ge2. The temperature dependence of the 73 Ge nuclear–spin–lattice-relaxation rate 1=T1 indicates the development of magnetic correlations and the formation of a Fermi-liquid state at temperatures lower than TFL ¼ 0:4 K, where 1=T1T is constant. The resistance and 1=T1T measured on an as-grown sample decrease below T onset c ¼ 0:2 K and T NQR c ¼ 0:1 K, respectively; these are indicative of the onset of superconductivity. However, after annealing the sample to improve its quality, these superconducting signatures disappear. These results are consistent with the emergence of unconventional superconducting fluctuations in close proximity to a quantum critical point from the superconducting to the normal phase in CeNi2Ge2.
6 citations
TL;DR: An antiferromagnet CeNiGe3, which exhibits a quantum critical point at P C ∼ 6 − 7 GPa, shows the superconductivity in wide pressure range of 1.7 − 9.3 GPa as discussed by the authors.
Abstract: An antiferromagnet CeNiGe3, which exhibits a quantum critical point at P C ∼ 6 – 7 GPa , shows the superconductivity in wide pressure range of 1.7 – 9.3 GPa . In addition to the superconductivity around P C , the sharp superconducting transition can be observed by both the resistivity and the susceptibility measurements at lower pressure region far apart from P C , where 4f-localized picture seems to be still dominant. Such a superconductivity is a first example in the f-electron systems.
5 citations
TL;DR: In this article, anisotropic resistivity in UIr has been investigated under high pressure for the measuring current parallel to the [0 1 0] direction while any anomalies were not observed in the resistivity for [1 0 1 ].
Abstract: Anisotropic resistivity in UIr has been investigated under high pressure. A huge enhancement of residual resistivity was found under high pressure for the measuring current parallel to the [0 1 0] direction while any anomalies were not observed in the resistivity for [1 0 1 ]. The residual resistivity for [0 1 0] reduced to the original value in the pressure range where superconductivity appears. This anomalous behavior indicates that the ground state in the high-ρ 0 state is not simple ferromagnet and the application of pressure induces the first-order transition to slightly different electronic state.
4 citations
TL;DR: In this paper, the results were compared with a bulk alloy made by the conventional method of melting, and the Curie temperature decreased with pressure at the rate of −6.9 and −8.0 K/GPa in MA and the bulk alloy, respectively.
4 citations
TL;DR: In this article, the de Haas-van Alphen (dHvA) measurement and the pressure experiment of the electrical resistivity for an antiferromagnetic magnet Ce 3 Sn 7 with the orthorhombic crystal structure were carried out.
Abstract: We carried out the de Haas–van Alphen (dHvA) measurement and the pressure experiment of the electrical resistivity for an antiferromagnet Ce 3 Sn 7 with the orthorhombic crystal structure. The detected dHvA branches are many in number and their dHvA frequencies are extremely small in magnitude, indicating that Ce 3 Sn 7 is a semimetal. This is consistent with the result of the energy band calculations under the assumption that the 4 f electrons of two Ce atoms in the 2( a ) site are localized and the 4 f electron of one Ce atom in the 4( i ) site is itinerant. In the pressure experiment, the Neel temperature of T N = 5.3 K is found to slightly increase with increasing pressure, becomes maximum around 1 GPa, then decreases steeply with further increasing pressure and most likely becomes zero between 3 and 4 GPa. The antiferromagnetic state is changed into the non-magnetic state under pressure.