Crystal structure and magnetic properties of the ternary rare earth metal-rich transition metallides RE14T3Al3 (RE = Y, Gd–Tm, Lu; T = Co, Ni)

The rare earth metal-rich RE14T3Al3 series (RE=Y, Gd–Tm, Lu; T=Co, Ni) have been prepared by arc-melting the rare earth metals with appropriate amounts of TAl precursors. All compounds crystallize in the tetragonal crystal system with space group P42/nmc in the Gd14Co3In2.7-type structure. Two structures (Y14Co2.78(1)Al3.22(1): a=952.99(4), c=2292.98(10) pm, wR2=0.0423, 2225 F2 values, 63 variables; Y14Ni3.07(2)Al2.93(2): a=955.06(5), c=2298.77(10) pm, wR2=0.0416, 2225 F2 values, 63 variables) have been refined from single-crystal data, indicating T/Al mixing on one crystallographic site. The lattice parameters of all members have been refined from powder X-ray diffraction experiments. The Y and Lu containing compounds for T=Co and Ni exhibit Pauli paramagnetic behavior, indicating that the Co and Ni atoms exhibit no localized magnetic moment in line with a filled 3d band. The other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Detailed magnetic investigations, however, were impossible due to the presence of e.g. RE3T trace impurities.

Magnetic Collapse and Insulator-Metal Transitions in Some 3D Metal Oxides Under High Pressures

In the systems with strong electron correlations, many theories predict the high-pressure-induced dielectric-metal transition, which is followed by collapse of localized magnetic moment and structural phase transition. In this report, summary results of many last experiments on the influence of high pressure on the magnetic and crystal structure as well on the electronic and transport properties of 3d metal oxides is presented. Along with X-ray diffraction, optical absorption, Raman scattering and electroresistivity measurements, several synchrotron radiation techniques have also been applied to perform the high-pressure experiments with compound iron oxides having different crystal structures.

NORMAL STATE MAGNETISM OF Zn-DOPED AND OXYGEN DEFICIENT CaLaBaCu3O7 SUPERCONDUCTOR

Both on-site Zn substitution and oxygen deficiencies in the CaLaBaCu 3 O 7 system decrease the superconducting transition temperature T c of the pristine sample. We observed that the normal state magnetism, measured in a field of 5 KOe, shows a Curie-Weiss behavior, in terms of a localized magnetic moment, presumably on Cu sites, in both cases. The pristine system, i.e. without Zn substitution or oxygen deficiencies, shows a weakly temperature dependent small magnetic susceptibility, in the normal state, i.e. above T c . It has been argued that the normal state magnetism of HTSC systems plays a vital role in determining the T c of these materials.