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|Title: ||Structure, crystal fields, magnetic interactions, and heavy-fermion behavior in (Ce1-xLax)(3)Al|
|Issue Date: ||2010-07-08 14:06:44 (UTC+8)|
|Abstract: ||We report measurements of the resistivity rho, susceptibility chi, and specific heat C of the alloys (Ce1-xLax)(3)Al. At room temperature these form in the hexagonal Ni3Sn structure (alpha-Ce3Al); at low temperatures a structural transition to a monoclinic phase occurs for 0 less than or equal to x less than or equal to 0.3 (gamma-Ce3Al); and a transition with a similar feature in the resistivity occurs for 0.75<x less than or equal to 1 (gamma-La3Al). Crystal fields have strong effects on these measurements: analysis of the specific heat suggests that for Ce3Al two excited doublets occur at temperatures T(lcf)approximate to 75 K and T(2cf)approximate to 130 K above the ground-state doublet, and that these splittings decrease significantly on alloying; this causes a similar decrease in the Curie-Weiss temperature theta(h) obtained from the high-temperature susceptibility chi=C/(T+theta(h)). The derivative d rho/dT of the low-temperature resistivity is negative over a range of temperature for all x (0 less than or equal to x<1), which is a characteristic sign of heavy-fermion (Kondo) behavior; various measures of the Kondo temperature T-K, taken from the analysis of rho, chi, and C, consistently suggest that T-K decreases by an order of magnitude on alloying, from approximate to 10 K for small x to approximate to 1 K for large x. Fits to the low-temperature specific heat which include a lattice contribution, a crystal-field contribution, and an S=1/2 Kondo contribution describe the data well for x=0.95; but for 0.3 less than or equal to x less than or equal to 0.82 the specific heat peak is larger and narrower than predicted by Kondo theory and a peak occurs in the resistivity, suggesting that coherence due to magnetic correlations plays a role for these concentrations. For the monoclinic phase, peaks in rho, chi, and C indicate antiferromagnetic order, where the Neel temperature decreases with x from its value T-N=2.5 K for x=0. The specific heat is linear at the lowest temperatures, even in the antiferromagnetic phase, which suggests that the magnetic order coexists with Kondo behavior.|
|Relation: ||PHYSICAL REVIEW B|
|Appears in Collections:||[物理研究所] 期刊論文|
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