Elastic, magnetic, and electrical properties of pure and lithium-doped nickel oxide

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Abstract
The measurement of Young's modulus as a function of temperature for pressure‐sintered lithium‐doped nickel oxide was found to be a very sensitive method for the determination of the variation of the Néel temperature with composition. The low‐temperature value of Young's modulus was found to increase with increased lithium content and the temperature of the modulus anomaly was found to decrease linearly with increased lithium content. This behavior was interpreted in terms of a localized electron theory of antiferromagnetism. Resistivity measurements agreed with the reported results on single‐crystal material. These include a break at the Néel temperature, a lower activation energy at higher temperatures than at lower temperatures, and a decrease in the low ‐ temperature activation energy with increasing lithium content. The combined trends in the modulus and resistivity as a function of temperature and impurity level were interpreted in terms of an electron‐acoustic‐mode interaction model which predicts an inverse relation between the elastic modulus and the energy difference between the self ‐ trapped and activated electron states. It was concluded that the success of a quantitatively correct localized electron model appears to depend on the development of a theoretical approach which would simultaneously account for both optical ‐ mode and acoustic ‐ mode interactions.

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