Tetsuo Kitai

Development of Miniature Diamond Anvil Cell for the Superconducting Quantum Interference Device Magnetometer

We have developed a novel miniature diamond anvil cell (mDAC) with a diameter of 8.5 mm and a length of 35 mm for a commercial superconducting quantum interference device (SQUID) magnetometer. In this mDAC, both X–Y and tilt adjustments of diamond anvil are possible. The SQUID magnetometer with this mDAC works under pressures higher than 1 GPa in a wide range of temperature and high magnetic field region. As for the test operation of this system, we first investigated the standard pressure effects of metallic superconductor Pb up to the pressure P = 3.8 GPa at the magnetic field H = 100 G and after that we investigated the pressure effect of an f-electron ferromagnetic compound GdZn2 up to P = 4.9 GPa for H ≤20000 G. The sensitivity of the present system is about 10-6 emu.

Non-Fermi Liquid Behavior in Dilute Quadrupolar System PrxLa1-xPb3 with x ≤0.05

We have studied the low-temperature properties of Pr x La 1- x Pb 3 with non-Kramers Γ 3 quadrupolar moments of the crystal-electric-field ground state, for a wide concentration range of Pr ions. For x ≤0.05, the specific heat C / T increases monotonically below T =1.5 K, which can be scaled with a characteristic temperature T * defined at each concentration x . The electrical resistivity ρ( T ) in the corresponding temperature region shows a marked decrease deviating from a Fermi-liquid behavior ρ( T ) ∝ T 2 . The Kondo effect arising from the correlation between the dilute Γ 3 moments and the conduction electrons may give rise to such anomalous behavior.

Magnetic and structural phase transition of CeCd at hydrostatic pressure

Abstract Hydrostatic pressure effects on the Curie temperature T c and two successive structural phase transition temperatures T M of CeCd were determined from both electric and magnetic measurements from 1.6 to 300 K at pressures up to 12 kbar. With increasing pressure, T c decreases, in contrast to the result of CeAg, and the T M s increase rapidly.

Low-Temperature Properties in Dilute Quadrupolar Compound PrxLa1-xInAg2

The low-temperature properties of Pr x La 1- x InAg 2 have been studied for a wide concentration range of Pr ions between 0≤ x ≤0.6. The susceptibility above T =15 K is well reproduced by the crystal-electric-field level scheme with a non-Kramers Γ 3 doublet in the ground state for each concentration, while that below T =15 K shows a non-Fermi-liquid behavior with a logarithmic temperature dependence. The temperature dependence of the specific heat C / T shows a monotonic enhancement below T =10 K, which can be scaled by a characteristic temperature T * defined at each concentration. These results suggest that the anomalous low-temperature properties are understood as the single-ion nature of Γ 3 quadrupolar moments. The origin of the anomalous properties is discussed in connection with the quadrupolar Kondo effect arising from the correlation between the Γ 3 moments and the conduction electrons.

Specific heat and electrical resistivity measurements in Pr0.03La0.97Pb3

Abstract We have measured specific heat C and electrical resistivity ρ for Pr0.03La0.97Pb3 with the Γ3 doublet in the crystalline-electric-field ground state to examine the Kondo effect arising from the correlation between the quadrupolar moments and the conduction electrons. It is found that C/T increases monotonically with lowering temperature below 1.5 K , which is clearly different from that in the Pr concentrated region. Moreover, ρ shows a clear drop below 3 K .

X-ray diffraction studies of LaCd, CeCd and PrCd at low temperatures

X-ray diffraction studies were made on LaCd, CeCd, and PrCd for temperatures between room temperature and 10 K. These compounds, which have the CsCl structure at room temperature, transform to structures with the tetragonal symmetry at low temperatures. On further cooling, satellite peaks having wave vectors (1/3, -1/3, 0) and (1/4, 1/4, 1/2) were found in CeCd below about 100 K. The symmetry of the lowest temperature phase is consistent with an orthorhombic structure. No new satellites were observed for PrCd, but the c / a -ratio changes abruptly at 20 K. The lattice instabilities associated with the phase transitions are discussed on the basis of a phenomenological model of lattice dynamics.

Nonlinear susceptibility measurement for quadrupolar response in a dilute Γ3 Non-Kramers Doublet System Pr0.05La 0.95Pb3

We measure the temperature dependence of the nonlinear susceptibility χ3, which reflects the fluctuation of quadrupolar moments, in Pr0.05La0.95Pb3 with a Γ3 non-Kramers doublet in the crystal-electric-field ground state to provide evidence of the quadrupolar Kondo effect. Non-Fermi liquid behavior of χ3 with a \(-\ln T\) dependence is detected in the [100] and [110] directions below \(T\approx 2.5\) K, suggesting the screening of quadrupolar moments. In contrast, χ3 in the [111] direction becomes constant below \(T\approx 3\) K. The observed features indicate that a low-lying Γ3 doublet plays a crucial role in the anomalous properties of PrxLa1-xPb3.

Field-induced magnetic transition in a single crystal of DyZn2

Abstract Temperature dependence of magnetic susceptibility and high field magnetism are studied for a single crystal of antiferromagnetic compound DyZn 2 . The paramagnetic Curie temperatures are anisotropic: Θ a p = 21.0 K, Θ b p = 38.4 K and Θ c p = −35.7 K. Different field-induced transitions are observed along each crystal axis direction.

Field-induced magnetic transitions in a single crystal of NdZn2

The measurements of the temperature dependence of magnetic susceptibility and magnetization in magnetic fields up to 150 kOe are carried out for a single crystal of NdZn 2 . Complex field-induced magnetic transitions occur for each direction of the crystal axes.

Lattice Modulation Induced by Magnetic Order in DyZn2.

DyZn 2 has an orthorhombic CeCu 2 -type structure. Between 29 K and the Neel temperature of 35 K, the magnetic structure is that of sinusoidal modulation characterized by a wavevector q m =ζ m c*, where ζ m is approximately 0.45 (MAF). The magnetic moments are parallel to the b -axis and, hence, the modulation is transverse. Below 29 K, the wavevector is 0.5 c* and the compound is a simple antiferro magnet. On this study, X-ray diffraction measurements were carried out on a single crystal of DyZn 2 . There is an anomaly in the thermal expansion at the Neel temperature, and satellite peaks were observed at 2 q m in the MAF phase. The amplitude of the lattice modulation u was observed to depend on ζ m . The fact that the lattice modulation has wavevector 2 q m has been examined on the basis of a model which takes into account modifications of the exchange interactions due to atomic displacements. Furthermore, the same model can explain the change of the thermal expansion. Measurements in magnetic fields up ...