Structure, spin glass, and spin state in perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x /spl les/ 0.5)
Perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x=0.2,0.3,0.4,0.5) compounds have been prepared by solid-state reaction. Structures were characterized using X-ray diffraction and Rietveld Refinement method. The compounds crystallized in orthorhombic with Plmn space group. Crystal lattices decreased with the increase of Mn doping level. DC magnetization and ac susceptibility were studied over a wide temperature range and different frequencies. A typical spin glass state was observed in all samples around the same temperature of 122 K where the compounds turned from paramagnetic to ferromagnetic states. For x<0.5, secondary transitions were observed both in dc and ac measurement which were independent of frequency but depended on doping level. The valences of Co or Mn with possible spin states were estimated.
Influence of the rare earth cation (Ln = La, Nd, Sm) on the properties of the Ln0.44Ho0.11Sr0.45MnO3±δ manganite oxides
Abstract The influence of the nature and the size of the rare earth cations on the structure, magnetic and transport properties of (La,Nd,Sm) 0.44 Ho 0.11 Sr 0.45 MnO 3± δ compounds are discussed. The samples were obtained by sol–gel methods and were investigated by means of X-ray diffraction, magnetic and electrical transport measurements. The sintered samples contained only one phase (tetragonal or orthorhombic). The unit cell volume, the average MnO distance and the microstrains decreased from the La to the Sm compounds. A diminishing of the specific magnetization and of the Curie temperature is associated with an increase of the degree of chemical disorder and a decrease of the tolerance factor. The transition temperature diminishes with the decrease of the tolerance factor, but the samples display a negative magnetoresistance behaviour in the investigated temperatures range.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.