| Autor: |
Zelinsky, A., Grin, Yu.N., Hiebl, K., Rogl, P., Noe¨l, H., Hilscher, G., Schaudy, G. |
| Zdroj: |
Journal of Magnetism and Magnetic Materials; 1995, Vol. 139 Issue: 1-2 p23-32, 10p |
| Abstrakt: |
A novel ternary solid solution U 1-y ▭ y (Ni 1-x Ga x ) 5 has been observed, whose homogeneous region at 800°C has been determined to range from 0.20 ≤ x ≤ 0.60 and 0 ≤ y ≤ 0.17 . Employing quantitative room-temperature, Rietveld-type X-ray powder analyses, the crystal structures of the novel solution range have been evaluated to be isotypic with the CaCu 5 -type for practically the entire homogeneity region. An enclave of alloys with an orthorhombically distorted unit cell has been observed in samples quenched from 800°C for x=0.45-0.55 and y≈0.09 . There are monotonic increases in the lattice parameters and in the volumes for nickel-rich alloys when nickel atoms at a constant U level are randomly replaced by gallium atoms in the 3g sites, whereas on further Ni/Ga replacement the nickel atoms preferentially occupy the prism centres at 2c, causing a maximum for the c -parameter at UNi 3 Ga 2 . The magnetic measurements for the gallium-rich compounds (x>0.5) show the typical broad maximum in the susceptibility at T≈60 K that is commonly observed in heavy-fermion systems. Furthermore, two samples exhibit an additional kink at T ≈ 26 K (T N ≈23 K ) possibly due to an antiferromagnetic coupling of the uranium spins. Anomalies in the specific heat versus temperature observed at 30.5 K for U 16.5 Ni 40 Ga 43.5 confirm the indications of the onset of AF magnetic order. The enhanced γ-value of ≈ 100 mJ/mol K suggests that this is a strongly correlated electron system. |
| Databáze: |
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