Toshio Mizushima

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.

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.

Magnetic Properties and Neutron Diffraction Measurements of Dense-Kondo Compound CeNi2Al5.

The intermetallic compound CeNi 2 Al 5 is an orthorhombic dense-Kondo compound with a magnetic transition temperature at 2.6 K. We have carried out magnetization and neutron diffraction measurements to study the magnetic structure of CeNi 2 Al 5 using a powder sample and a single crystalline sample. It is found that the magnetic structure is sine-wave modulated with a propagation vector k =(1/2,2/5,1/12). The maximum amplitude of magnetic moment is equal to 1.54 µ B and its direction is tilted 8 degrees from the b -axis toward the a -axis.

Origin of Weak Ferromagnetism in YbxFe4Sb12, Relationship between Weak Ferromagnetism and Filling Ratio x

The magnetization and specific heat of single-crystalline samples of filled-skutterudite compounds Yb x Fe 4 Sb 12 were measured. Six single crystals with the filling ratio of Yb, x , from 0.875 to 0.910 were prepared. The weak ferromagnetism of Yb x Fe 4 Sb 12 appearing at low temperatures was found to strongly correlate with x ; with increasing x from 0.875 to 0.910, the transition temperature, T C , decreases from 17 to 5 K and the weak-ferromagnetic moment, m 0 , decreases from 0.066 to 0.005 µ B /Fe. From these trends, both T C and m 0 were expected to reach zero at the critical concentration, x c =0.93. In the temperature dependence of the specific heat, no anomaly at T C was observed, reflecting that m 0 is extremely small compared with the effective Bohr magneton number. With the application of pressure, the T C of the sample with x =0.882 increases rapidly, with the ratio of d T C /d P =+5.27 K/GPa. This weak ferromagnetism of Yb x Fe 4 Sb 12 originates from the itinerant 3d electrons of Fe in an...

Dense Kondo Effect in Caged Compound CeRu2Zn20

We prepared single crystals of the caged compound CeRu2Zn20 by the flux method, and measured the magnetization, magnetic susceptibility, specific heat, and electrical resistivity. The lattice constant measured at room temperature suggests that the Ce ion is trivalent in this compound. The temperature dependence of magnetic susceptibility obeys the Curie–Weiss law with the effective Bohr magneton of Ce3+ at high temperatures. However, at low temperatures, CeRu2Zn20 indicates no phase transition down to 2 K and shows typical behaviors of a heavy Fermion system; the enhanced magnetic susceptibility χ0, the enhanced electronic specific-heat coefficient γ0, and the electrical resistivity with the temperature dependence of \(AT^{2}\), although these parameters somewhat depend on samples. The Wilson ratio \(R_{\text{W}}\) of χ0/γ0 is approximately 2, which does not depend on samples. A/γ0 is plotted on the line of \(N = 2\) in the new Kadowaki–Woods plots. The Kondo temperature \(T_{\text{K}}\) is roughly estima...

Magnetic Structure of PrNiAl4.

Neutron powder-diffraction measurements of PrNiAl 4 were carried out at temperatures above and below the Neel temperature of 8.4 K. The antiferromagnetic structure was determined; the propagation vector is (010), and the magnetic moment is 2.59µ B along the a -axis. This magnetic structure is consistent with the results of magnetization and magnetic susceptibility measurements on a single crystalline sample.

Magnetic, Electric and Thermal Properties of NdNiAl4 Single Crystal.

The electrical resistivity, magnetization, specific heat and thermoelectric power measurements were performed on a NdNiAl 4 single crystal along the principal axes of the orthorhombic cell. The easy axis of magnetization was parallel to the b axis below 20 K. The spin-flipping was observed at the magnetic field 4.4 T along the b axis at 2 K. The magnetic phase diagram was determined from the spin-flipping field. The huge magnetic anisotropy energy was estimated from the experiments of the magnetic susceptibility and magnetization. The energy gap newly occurred below T N was observed in the electrical resistivity along the b axis. From this result we have speculated that a new magnetic periodicity is made along the b axis below T N . The magnetic susceptibility for the principal axes was discussed on the bases of the crystalline-electric-field and molecular-field theories.

Mössbauer Effect and Magnetization Studies of YbFe4Sb12 and LaFe4Sb12

We prepared two YbFe 4 Sb 12 samples (#1 and #2) and a LaFe 4 Sb 12 sample. Mossbauer and magnetization measurements were performed on the samples at various temperatures and in applied magnetic fields. The experimental results indicate that #1 is in a weakly ferromagnetic state below 13 K, while #2 is in an itinerant paramagnetic state even at 2 K, and that quadrupole splitting for #1 at each temperature is slightly less than that for #2. Therefore, we conclude that YbFe 4 Sb 12 is an intermediate material between a nearly ferromagnetic material and a weakly ferromagnetic material.