Yosikazu Isikawa

A New Dense-Kondo Compound CeNiAl4

Experiments of electrical resistivity, specific heat and magnetic susceptibility of a ternary intermetallic compound CeNiAl 4 have been carried out. It is found that CeNiAl 4 is a new member of the dense-Kondo compounds in the valence-fluctuation regime and that CeNiAl 4 is nonmagnetic above 1.6 K. The susceptibility χ 0 and the electronic specific heat coefficient γ 0 which are extrapolated to 0 K are 5.6×10 -3 emu/mol and 204 mJ/mol·K 2 , respectively. The Kondo temperature T K is estimated to be 67 K or 86 K.

Electrical Resistivity, Magnetic Susceptibility and Specific Heatof a New Dense Kondo Compound CeNi2Al5

The electrical resistivity, magnetic susceptibility and specific heat of a ternary intermetallic compound CeNi 2 Al 5 have been measured. It is found that CeNi 2 Al 5 is a new dense Kondo compound with the Neel temperature of 2.6 K. The temperature dependence of the resistivity has a broad peak at 4.0 K, reflecting the coherence of the Kondo scattering. The ground state of the Ce ions is determined to be a doublet from the result that the entropy equals R ln 2 when we include the area of a tail extended by the short-range order. A spin-flip is observed in high magnetic field, and a magnetic phase diagram is roughly estimated.

Magnetic Properties of the Dense Kondo Compound YbNiSn

Specific heat measurements revealed that YbNiSn is a dense Kondo compound with a large electronic specific heat coefficient γ of 300 mJ/mol K 2 . This compound orders magnetically at 5.5 K, below which the ferromagnetic moment appears along the c -axis. The magnetization along the a -axis vs external magnetic field H curve shows three anomalies at H C1 , H C2 and H C3 , whereas the magnetization along the b -axis increases gradually from zero without anomalies. These results suggest that YbNiSn is the weak ferromagnet with the ferromagnetic moment along the c -axis, which is caused by the canting of antiferromagnetic sublattice within the ac -plane. The magnetic field dependences of the electrical resistivity of YbNiSn are strongly correlated with the magnetizations.

Formation of Kondo lattice in La1−xCexNi

Temperature dependences of the resistivity and the susceptibility of single crystals of solid solution La 1- x Ce x Ni have been measured in the temperature range 2–300 K. We have obtained a phase diagram of La 1- x Ce x Ni which is consisted of three parts; (1) isolated Kondo region ( x 0.6 and high temperature region), where the 4f electron behaves as fairly localized electron although the valence of the Ce ion is more than three and (3) Kondo lattice region ( x >0.6 and low temperature region), where the 4f state becomes a delocalized state.

Quasi-One-Dimensional Antiferromagnetic Correlation in the Kondo Semiconductor CeNiSn

Spin excitation of the Kondo semiconductor CeNiSn has been studied by neutron scattering in a wide Q space. Below the coherence temperature of 20 K, the excitation spectra show pronounced peaks at \(\hbar\omega = 4\) and 2 meV, at \(Q=(Q_{a}, \frac{1}{2}, Q_{c})\) and (0 0 1), respectively. The observed Q dependence of the 4 meV excitation implies that the corresponding dynamical antiferromagnetic-correlation is quasi-one-dimensional along the b -axis, and is polarized mainly along the a -axis.

Magnetic properties of NdFeO3 single crystal in the spin reorientation region

High quality NdFeO3 single crystal has been grown by the four-mirror image floating zone technique. The magnetic properties and specific heat of NdFeO3 single crystal were systematically studied in the temperature range from 2 to 300 K. A clear spin reorientation behavior is observed in a wide temperature range from 100 to 170 K, with the gradual transition of the Fe3+ magnetic moment ordering from {Gz, Mx}-type ordering at low temperatures to {Gx, Mz}-type ordering at high temperatures. In the temperature range from 170 to 300 K, the value of Mx is not equal to zero. It is assumed a single {Gx, Mz}-type ordering mixed with {Gxz, Mxz}-type orderings. During the spin orientation transition process, the hysteresis loops become narrow with very small coercivity. Based on the specific heat measurement, the Schottky anomaly at very low temperature and the thermal anomalies induced by the spin reorientation were also discussed.

High Field Magnetoresistance and de Haas-van Alphen Effect in CeNi

We have measured the magnetoresistance and de Haas-van Alphen (dHvA) effect in CeNi in the field up to 150 kOe and at temperature down to 0.4 K. This material is found to be a compensated metal with equal carrier concentration of electrons and holes. The open orbits exist along the b - and c -axes. Four dHvA branches have been found in the field along the b -axis. The dHvA frequencies and the cyclotron masses are 3.60 ×10 7 Oe (10.3 m 0 ), 1.25 ×10 7 Oe (8.91 m 0 ), 6.58 ×10 6 Oe (3.05 m 0 ) and 2.15 ×10 6 Oe (2.58 m 0 ).

Correlation between the specific heat and high field magnetism of La1−xCexNi at low temperatures

Abstract The specific heat of La 1− x Ce x Ni has been measured from 1.3 to 4.2 K and high field magnetization was measured in magnetic fields up to 100 kOe at 4.2 K. The correlation between the specific heat coefficient and the susceptibility at low temperatures was discussed on the basis of the Fermi liquid theory.

Application of Doniach Diagram on Valence Transition in EuCu2(SixGe1-x)2

To investigate the valence transition of Eu in the pseudo-binary compounds series, EuCu 2 (Si x Ge 1- x ) 2 , measurements of the lattice constants, the X-ray absorption spectroscopy (XAS), the mag...

Thermal conductivity, electrical resistivity and specific heat of high-Tc Ni1.4Pb0.6Sr2Ca2Cu3Ox superconductor

Abstract The sharp superconducting transition temperature, T c , end =105K was obtained from the measurement of electrical resistivity for the sample of Bi 1.4 Pb 0.6 Sr 2 Ca 2 Cu 3 O x . The thermal conductivity showed a striking increase below T c as similar to those of LnBa 2 Cu 3 O 7−y superconductors. The low temperature specific heat was measured below 10K. Since C Tvs.T 2 curve is nearly linear above 5K, assuming C T = γ+z( 1944 Π 3 D )T 2 , the values of γ and Π D are estimated as 9.5 mJ/mole·K 2 and 220K, respectively.