Abstract
In this paper we report the investigation on the formation, if any. of supersaturated solid solution by mechanical alloying of Cu-20% Co and by hydrogenation of Pr(Co,Cu)5 intermetallics. A comparative analysis of structure and magnetic properties of above mentioned systems are performed.
The structural state of Cu80Co20 system after mechanical alloying and a subsequent thermal treatment has been studied by NMR-spectroscopy and X-ray diffraction. Analysis of the data obtained as well as magnetic and magnetoresistive properties make it possible to assume the formation of ultradispersed cobalt clusters in a copper matrix. A partial dissolving of cobalt in copper is likely to take place in defect regions. Such a structure is responsible for superparamagnetism 0of Cu80Co20 system at T > 150 K and for a considerable giant magnetoresistance (GMR) effect (12% at T = 77 K). A shift of X-ray peaks of a copper matrix can partially be due to a coherence of Cu and Co phases.
Quasi-binary Pr(Co1-x Cu x )5 intermetallics with 0 ≤ x ≤ 1 were hydrogenated at elevated temperatures to precipitate Co and Cu and to study their mutual solubility. Low temperature hydrogenation was found to form a CaCu5-type hydride containing about 1.6 hydrogen atoms per formula unit. Above 500°C the sample decomposed into PrH2.6, Cu and HCP-Co. In the temperature range 330 - 450°C the CaCu5-type hydride coexisted with the decomposed phases. Structural and magnetic measurements indicated that no solid solution was formed in Co-Cu decomposed phases. The magnetoresistance on both parent and hydrogenated samples did not exceed 0.5%.
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Yermakov, A.Y. et al. (1998). Magnetic State, Transport Properties and Structure of Granular Nanophased Systems. In: Chow, GM., Noskova, N.I. (eds) Nanostructured Materials. NATO ASI Series, vol 50. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-5002-6_21
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DOI: https://doi.org/10.1007/978-94-011-5002-6_21
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