We report the investigations of crystal structure, electrical resistivity (ρ), magnetization (M), specific heat (C P ), thermal conductivity (κ), and thermoelectric power (TEP) on La 0.7 Sr 0.3 (Mn 1-x Ru x )O 3 (LSMRO) compounds with x = 0 to 0.90. From the analyses of crystal structure and magnetization measurements, it is inferred that Ru should have a mixed valence of Ru 3+ and Ru 4+ for LSMRO with low level of Ru substitution, and an additional mixed valence of Ru 4+ and Ru 5+ with higher Ru substitution. It is found that all measured physical properties undergo pronounced anomalies due to the ferromagnetic-paramagnetic phase transition, and the observed transport properties of LSMRO can be reasonably understood from the viewpoint of polaronic transport. The Curie temperatures T C determined from the magnetization measurements are consistently higher than those of the metal-insulator transitions T MI determined from the transport measurements. By replacing Mn with Ru, both T C and T MI decrease concurrently and the studied materials are driven toward the insulating phase with larger value of x. It is also found that the entropy change during the phase transition is reduced with more Ru substitution. These observations indicate that the existence of Ru has the effect of weakening the ferromagnetism and metallicity of the LSMRO perovskites.

No abstract

Nucleation experiments (metastable zone width) were carried out for 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) solutions at different saturation temperatures with and without the addition of a chelating agent. Using the results obtained from metastable zone width experiments, the slope nucleation method growth of DAST was performed. It was revealed that the addition of the chelating agent EDTA significantly suppresses spurious nucleation and cluster formation in the DAST solution, so that fewer, but larger, crystals can be easily obtained. With EDTA, the crystals grown also showed better crystallinity, hardness, and transparency in the visible/near-infrared region.

No abstract

The magnetic ordering of the Mn spins in polycrystalline Nd0.62Ca0.38MnO3 has been investigated by means of neutron diffraction and ac magnetic susceptibility measurements. Three peaks around 230, 90, and 40 K were observed in the temperature dependence of the in-phase component of the ac susceptibility, χ′(T). Neutron diffraction measurements show that the peak at 90 K is associated with the ordering of the Mn spins, and that at 40 K is due to the reorientation of the Mn spins. Both ferromagnetic and antiferromagnetic coupling between the Mn spins were observed. The spins order at TN≈130 K, with a spin structure consisting of ferromagnetically coupled, tilted antiferromagnetic sheets. No evidence was found from the neutron diffraction data to indicate that the peak around 230 K in χ′(T) is of magnetic origin, which suggests that it is associated with charge ordering.