We report measurements of the thermoelectric power (TEP) on the La0.65Ca0.35Mn1−x FexO3 system for 0.00 ≤ x ≤ 0.07. The ferromagnetic and metallic transition temperatures are lowered and the TEP shows an increasingly positive trend with the addition of Fe. We also observe a clear magnetic contribution that manifests itself as a peak in the TEP close to the critical temperature. The activation energies determined from the TEP are seen to be insensitive to the Fe content. The data are interpreted firstly as showing a decrease in the density of active holes, i.e. holes that can participate in the hopping process, with increasing Fe content. Secondly the data suggest the role of magnetic scattering due to the clusters formed by the antiferromagnetically coupled Fe. Abrupt changes in the variation of the TEP are observed at the concentration region x ∼ 0.04 consistent with the hole density variation and with previously reported transport and magnetic measurements.

The Sm0.50Sr0.50MnO3 system has been studied with respect to identifying the various electronic and magnetic phases and the effects of introducing different cation dopants on these phases and their respective stabilities. Magnetic, resistive and thermoelectric studies have been performed as a function of temperature in Sm0.50Sr0.50MnO3, (Sm0.50Nd0.50)0.50Sr0.50MnO3 and Sm0.50(Sr0.50Ca0.50)0.50MnO3. The parent compound (Sm0.50Sr0.50MnO3) lies close to the ferromagnetic–antiferromagnetic (FM–AFM) phase boundary and the consequent effects of the dopants are explained in terms of the changes in the one electron bandwidth and the cation size variation and disorder. Below 130 K the ground state for Sm0.50Sr0.50MnO3 composition is seen to be a mixture of ferromagnetic and A-type antiferromagnetic phases. Partial substitution of a larger size cation (Nd) in place of Sm raises the ferromagnetic transition temperature while at the same time stabilizing the AFM phase. This latter trend is inferred from the differences in the hysteresis behaviour of the two systems and is explained in terms of the decrease of the size mismatch factor between cations. However, partial substitution of the smaller size cation (Ca) in place of Sr almost eliminates the ferromagnetic phase, leaving the system in a charge ordered state, which appears to be accompanied by the CE type of charge–orbital ordering, exhibiting extremely large values of resistivity.

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Metrology is the science of measurement. The chapter contains introductory material, terminology and units used in the optical radiation metrology. Optical radiation metrology provides an applied understanding of essential optical measurement concepts, techniques and procedures. In this chapter, we focus on electromagnetic radiation with wavelengths from approximately 100 to 2500 nm. We describe the principles used to measure photometry and radiometry quantities such as total flux, intensity, illuminance, luminance, radiance, exitance and irradiance. Measurement results should be expressed in terms of estimated value and an associated uncertainty, we provide an explanation to how to estimate and build the uncertainty budget of measurements. Metrology is based on measurements and comparisons. The unit is a unique name we assign to the measures of that quantity. Base standards must be both accessible and invariable. The metrological traceability chain is the sequence of measurement standards and calibrations that were used to relate the measurement result to the reference. The uncertainty budgets for photometric and radiometric quantities are represented in this chapter.

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