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Giant negative thermal expansion covering room temperature in nanocrystalline GaNxMn3.
- Source :
- Applied Physics Letters; 9/28/2015, Vol. 107 Issue 13, p1-5, 5p, 5 Graphs
- Publication Year :
- 2015
-
Abstract
- Nanocrystalline antiperovskite GaN<subscript>x</subscript>Mn<subscript>3</subscript> powders were prepared by mechanically milling. The micrograin GaN<subscript>x</subscript>Mn<subscript>3</subscript> exhibits an abrupt volume contraction at the antiferromagnetic (AFM) to paramagnetic (PM) (AFM-PM) transition. The temperature window of volume contraction (ΔT) is broadened to 50 K as the average grain size (〈D〉) is reduced to ~30 nm. The corresponding coefficient of linear thermal expansion (α) reaches ~ -70 ppm/K, which are comparable to those of giant NTE materials. Further reducing 〈D〉 to ~10 nm, ΔT exceeds 100 K and α remains as large as -30 ppm/K (-21 ppm/K) for x = 1.0 (x = 0.9). Excess atomic displacements together with the reduced structural coherence, revealed by high-energy X-ray pair distribution functions, are suggested to delay the AFM-PM transition. By controlling 〈D〉, giant NTE may also be achievable in other materials with large lattice contraction due to electronic or magnetic phase transitions. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00036951
- Volume :
- 107
- Issue :
- 13
- Database :
- Complementary Index
- Journal :
- Applied Physics Letters
- Publication Type :
- Academic Journal
- Accession number :
- 110121602
- Full Text :
- https://doi.org/10.1063/1.4932067