Magnetic, specific heat and transport properties of U1-xThxPt alloys

H. Tran V, A. Czopnik, P. D.V. Du Plessis, A. M. Strydom, R. Trać, V. Zaremba

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4 Citations (Scopus)


Previous studies on UPt samples indicated ferromagnetic ordering either at TC = 27 K or at TC = 19 K while in some samples there was evidence of the presence of both these transitions. These differences are thought to be associated with the presence of material of different crystal structure, viz. a monoclinic structure for the higher-TC material (H phase) and an orthorhombic structure for the lower-TC material (L phase). We have studied the crystal structure, magnetization, specific heat and transport properties of the solid solutions U1-xThxPt, including a pure UPt sample. We observed that the substitution of Th for U in UPt stabilizes the L phase for all compositions. Ferromagnetism is observed for 0 ≤ x ≤ 0.4 and there are indications of the presence of short-range magnetic order for x ≥ 0.5, which vanishes slowly up to x ≈ 1. At low temperatures in the magnetically ordered region the magnetic and electronic contributions to the specific heat C5f and electrical resistivity ρ5f are described by expressions that contain the magnon energy-gap Δ. These also include the γ5f(0)T and AT2 terms to describe the C5f and ρ5f temperature dependences respectively. For L-phase UPt, the low-temperature fitting (below 10 K) yields Δ = 19(1) K and γ5f(0) = 0.122(2) J K-2/mol U, while the higher-temperature one (above 10 K) yields Δ = 35(2) K and γ5f(hT) = 0.151(3) J K-2/mol U. With Th substitution Δ decreases, but the γ5f(0) value for both the magnetically ordered and non-ordered samples remains practically unchanged, being close to that of the higher-temperature value found for this compound. The magnetoresistance is negative and large in the ordered region and becomes slightly positive at low temperatures for the Th-rich alloys. The presence of the Kondo interaction is indicated in these alloys almost up to x ≈ 1.

Original languageEnglish
Pages (from-to)9897-9916
Number of pages20
JournalJournal of Physics Condensed Matter
Issue number48
Publication statusPublished - 4 Dec 2000
Externally publishedYes

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics


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