PIXE and magnetic investigations of La_xRe_(1-x)F_3 (RE = Ce, Nd) single crystals

摘要

The mixed La_xRE_(1-x)F_3 (RE = Ce, Nd) single crystals doped with Gd~(3+) (0.1 mol%) were grown by a modified Bridgmann-Stockbarger method. The PIXE (Proton Induced X ray Emission) method was used to the determination of a composition x of this material. The value of x for these samples does not differ more than 2.5 % and 7.5 % in La_xCe_(1-x)F_3 and La_xNd_(1-x)F_3 respectively, from the assumed one. In addition, concentrations of the doped rare earth atoms were controlled by XRF (X-Ray Fluorescence) method. The abundance of other than Gd~(3+) rare earth impurities was estimated to be below 0.058 at.%. The magnetic susceptibility of the single crystals was measured in the temperature range 4 - 300 K, in a magnetic field B = 0.2 T applied in the crystallographic plane (001) perpendicular to the c-axis (along the a-axis), using the Faraday method. The magnetic susceptibility measurements confirm the lack of Ce~(3+) and Nd~(3+) clusters in the diluted crystals. The effective spins of hosts Ce~(3+) and Nd~(3+) are equal to 1/2 in the temperature range 4 - 300 K.