Ikuji Tsujikawa

Absorption Spectra of Cr3+ in Al2O3 Part B. Experimental Studies of the Zeeman Effect and Other Properties of the Line Spectra

The absorption intensities, widths and wave-numbers of R 1 , R 2 and B 1 B 2 lines of Cr 3+ in ruby for the polarized light E ⊥ C 3 and E // C 3 are experimentally studied at 20°K and 4.2°K. Zeeman effect is also studied, using a magnetic field H 0 =24,000 φ, for both R and B lines. The Zeeman effect has not been observed yet for the B lines, while Lehmann has already observed the Zeeman effect for R lines. In our results of R lines, the quantitative aspects of Lehmanns experiment are improved. The comparison is made with the theoretical results given in Part A and it is shown that nice agreements can be obtained when suitable assignments of the spectra are adopted and when fairly large g -shifts of the excited states are introduced.

Superconductivity in graphite–potassium intercalation compounds

Superconductivity transitions were studied in golden graphite−potassium compounds. The transition temperature changes were studied by adding hydrogen to the compound. (AIP)

Magnetic and Transport Properties of Ce-Ta-S Ternary System

Synthesis, transport and magnetic properties of a new ternary system Ce-Ta-S have been investigated. (CeS) 0.6 TaS 2 and (CeS) 1.2 TaS 2 order antiferromagnetically with Neel temperatures of 2.3 K and 2.7 K, respectively. In the former compound, a diverging anomaly in the susceptibility at T N , a small spontaneous magnetization below T N and a magnetic phase transition at 2.5 kOe are observed. From these results, (CeS) 0.6 TaS 2 is supposed to be a quasi-2D antiferromagnet with a weak ferromagnetism composed of ferromagnetic layers. The fractional superconductivity is observed with the magnetic ordering. Ce 4 f electrons are well localized and the correlation between Ce 4 f and conduction electrons is weak in these compounds.

Absorption Lines of Manganous Fluosilicate Hexahydrate

The Zeeman effect and the dilution effect of absorption lines in the violet region of MnSiF 6 ·6H 2 O were measured at low temperatures between 20°K and 1.2°K with a spectrograph with 2.6A/ mm dispersion in order to complete the analysis of the spectra. The properties of the excited state for sharp quartet lines between 24,918 cm -1 and 24,953 cm -1 became clear in some detail. The singlet line at 25,043 cm -1 which was isotropic in the absence of a field became anisotropic when a magnetic field was applied. These anisotropies may be explained assuming magnetic dipole transitions. As a result, it is concluded that the quartet lines and the singlet line correspond to transitions from the ground state 6 A 1 to the excited states 4 E and 4 A 1 , respectively. Assuming the frequencies of the three odd ligand vibrations, the other broad lines in the shorter wave length region can well be interpreted as the transition coupled with these vibrations. An observation of the shifts of the quartet lines and the singl...

Theoretical studies on the isolated spin cluster complex, tetrameric cobalt (II) acetylacetonate Co4(C5H7O2)8: Effects of competing superexchange interactions

According to x‐ray studies, Co4(C5H7O2)8 is an assembly of linear, tetrameric Co2+ ion clusters, which are effectively magnetically isolated. An examination of superexchange paths suggests that this tetramer has two different kinds of nearest‐neighbor exchange constants plus a next‐nearest‐neighbor exchange constant. The only bulk experimental data available so far are the powder susceptibilities from room temperature down to about 0.35 K. This paper demonstrates that this information is apparently sufficient to infer that all three exchange constants are antiferromagnetic in type and have values in the region of Jnn1 ∼ 5 K, Jnn2 ∼ 10 K, and Jnnn3 ∼ 4 K. The interactions therefore compete; and they compete so as to give a paramagnetic character to the low temperature behavior. This is in interesting contrast to the behavior of a sister compound, trimeric nickel (II) acetylacetonate, where the paramagnetic character results from a dominant nearest‐neighbor ferromagnetic exchange constant. The exchange cons...

Transport and superconducting properties of potassium hydride graphite intercalation compounds

Abstract Potassium hydride graphite intercalation compounds were prepared by the direct intercalation of potassium hydride into HOPG and their structures were confirmed by (00l) X-ray diffraction. The resistivity of the stage-1 to -3 compounds were presented as a function of temperature. As a preliminary measurement of susceptibility, the diamagnetism attributed to superconductivity was detected in the stage-2 C8KHx, which increases continuously from 360mK down to 70mK.

Absorption Lines of Manganous Acetate Tetrahydrate

Five sharp absorption lines of Mn(CH 3 COO) 2 ·4H 2 O were found in the violet region at liquid helium temperature. The line at 24,496 cm -1 and the quartet lines between 24,695 cm -1 and 24,770 cm -1 were assigned to the transitions from the ground state 6 A 1 to the excited states 4 A 1 and 4 E respectively. These transitions are caused by an electric dipole. The magnetic field dependence of relative intensities of these lines at 1.3°K was investigated, and it was concluded that the ordered state below 3.18°K is ferrimagnetic, that the preferred axis is the a axis and that the most difficult axis is the b axis. The results of susceptibility measurements and electron spin resonance were consistent with the present conclusion.

Optical absorption spectra in the quasi-two-dimensional antiferromagnets (NH3(CH2)nNH3)MnCl4 (n=2, 3, 4, 5). I. Experimental

Optical absorption spectra in the quasi-two-dimensional antiferromagnet (NH3(CH2)nNH3)MnCl4 (n=2, 3, 4, 5) were investigated. In the transitions 6A1g(S) to 4A1g(G), 4Eg(G), 4T2g(D), 4Eg(D) and 4T1g(P), much fine structure caused by electric dipole transition appeared at low temperature. It was concluded that fine structure resulted from magnon-assisted transitions by taking into account the temperature dependence of the spectra. In these compounds, when an external magnetic field was applied along the spin easy axis, a drastic energy shift in the spectra was observed at the spin-flop transition (H0=25-35 kOe). The authors reveal the origin of these spectral changes and classify the optical absorption spectra by their original excitons, taking into account these spectral changes. It is concluded that the analysis of the spectral shift at the spin-flop transition is one of the most powerful methods to assign the absorption spectra in these antiferromagnetic compounds. Spectral changes under uniaxial stress were also investigated.

Synthesis, transport and superconducting properties of rare earth metal intercalated tantalum disulfide RExTaS2 (RE=La,Ce)

Abstract The new intercalated systems RE x TaS 2 (RE=La,Ce) were prepared and their transport and superconducting properties were investigated. Different preparation methods provided four phases (α, β, γ and δ) which could be classified according to their structure forms. The temperature dependence of the resistivity had a minimum at 35K and 23K for La and Ce intercalated samples (phase γ), respectively. By the AC susceptibility measurement, the superconductivity was detected in the La 16 TaS 2 (phase α) and Ce intercalated sample (phase δ). A large paramagnetic signal was observed in the latter compound above the transition temperature 1.7K.

Electrical resistance and its variation during intercalation in the FeCl3-graphite system

Abstract The measurement of the in-plane electrical resistivity ( ϱ a ) was undertaken using a four-point d.c. procedure in the temperature range from the reaction temperature to 77 K for FeCl 3 -graphite compounds. The measurement of the change of the in-plane electrical resistance during intercalation was also made. The use of grafoil as host led to the following distinctive features. 1. (1) The dependence of ϱ a on the concentration of FeCl 3 at room temperature, and the temperature dependence of ϱ a for the low stage compounds, were both greater than those where HOPG (highly oriented pyrolytic graphite) was the host graphite. 2. (2) The sample with 1.2 mol% of FeCl 3 was of metallic nature, while the sample of grafoil was semiconductive at all observed temperatures, so that a type of metal-semiconductor transition took place at an FeCl 3 concentration threshold value of less than 1.2 mol%. 3. (3) The usual metal-semiconductor transition took place around 300 K for the sample with 0.8 mol% of FeCl 3 . 4. (4) A higher reaction rate was obtained than when using natural graphite.