Title

Anomalous Thermal Expansion in Substituted Nd₂Fe₁₇₋ₓSiₓ and Nd₂Fe₁₇₋ₓAlₓ Compounds

Abstract

The temperature dependencies of the lattice parameters were measured from room temperature to 400 °C for powders of the substituted compounds Nd2Fe17-xAlx and ND2Fe17-xSix = 0,1,2,3, using high-temperature x-ray diffraction. All compounds crystallize in the rhombohedral Th2Zn17-type structure (space group R3-m). Invar-type anomalies are found in the temperature dependence of a and c below the Curie temperatures, Tc, but featuring different substitution effects of Fe by Al and Si atoms, respectively. The Nd2Fe17-xAlx and ND2Fe17-xSix compounds retain easy-plane anisotropies upon substitution up to x = 3. Therefore, the observed spontaneous volume magnetostrictions are due mainly to the isotropic exchange contribution of the iron sublattice. According to the localized model of exchange interactions in R-Fe compounds, the different substitution effects can be ascribed to the different preferential occupation tendencies of Al and Si atoms on the sites of the Th2Zn17-type structure.

Department(s)

Chemistry

Second Department

Physics

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1995 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.


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