H. Deguchi

Magnetism of one-dimensional copper oxides related to HTSC

Abstract Magnetic and electronic properties of two kinds of copper oxides with the linear chains linked by planar CuO 4 , Ca 2 CuO 3 and Li 2 CuO 2 , were investigated by magnetic susceptibility (χ), specific heat ( C p ) and XPS measurements. Ca 2 CuO 3 has scarcely any magnetic contribution to χ and C p in striking contrast with Li 2 CuO 2 which shows 3D-AF magnetic ordering at 9.3 K. They are discussed on the linear chain model.

Thermal and magnetic properties of M(HCOO)2·2urea: M=Mn, Fe, Co, Ni

Abstract Properties of newly synthesized quadratic AF are summarized. T N =3.77 K (Mn), 7.9 K (Fe), 6.34 K (Co), 15.0 K (Ni). Their usefulness comes from their moderate magnitude of exchange and is exemplified with heat capacity and magnetization measurements.

Thermodynamical study of the magnetic transition in commensurate phases in PrCo2Si2

Abstract In the magnetically commensurate phases in the axially anisotropic compounds PrCo 2 Si 2 , the paramagnetic ions with individual entropy k B ln 2 has been detected to be immersed regularly by the heat capacity measurement and the adiabatic magnetization experiment. The possibility of the phase-slipping of the sinusoidal exchange field has been suggested to be driven by the variation of temperature in zero field.

Heat capacities of helium in one- and three-dimensional channels at low temperatures

Heat capacities of Ne adsorbed in the one- and three-dimensional channels in the high-silica zeolites ZSM-23 and ZSM-5 have been observed in the temperature range from 2 K to 23 K for various concentrations of Ne. For lower concentrations of Ne, the low-temperature heat capacities for both the one-dimensional and the three-dimensional channels, both about 5.5 AA in diameter, are described by the Einstein model, which implies that Ne atoms are localized independently or construct clusters of minute size in the channels. However, for the higher concentration where channels are nearly filled with Ne atoms, the heat capacities of Ne reflect the difference between the topological channel structures of the two zeolites. In the case of three-dimensional channels, the heat capacity is revealed to be well reproduced by the Debye model for a continuous solid with the characteristic temperature Theta D=29 K, which is unexpectedly smaller than the values Theta 3D approximately=67 K for the bulk solid Ne and Theta 2D approximately=50 K for the two-dimensional solid Ne. This suggests the possibility of an unusual softening effect of phonons in solid of Ne in the three-dimensional network of channels. While the heat capacity of Ne in the one-dimensional channels cannot be understood in terms of the one-dimensional Debye model, it can be explained using the Einstein model. These results for the classical Ne particle are significant when compared with the thermal behaviour of He in the same zeolites, which reflects the characteristic quantum effect at low temperatures.

NMR study of random mixture with competing interactions: Co1−xMnxCl2·2H2O

Abstract In proton NMR spectra, the satellite line due to the moments of spin glass state is observed in the reentrant spin glass phase. The strong temperature dependence of the NMR intensity suggests the easy change between the long-range ordered region and the spin glass region. The nuclear spin lattice relaxation times do not show any anomalies at the transition temperature to the antiferromagnetic phase because of the long relaxation time of the freezing spins.