Low-temperature specific heat of uranium germanides
Journal of Magnetism and Magnetic Materials(2014)
摘要
We report measurements of the specific heat down to the lowest temperature of 2K for the paramagnetic binaries U5Ge4 (Ti5Ga4-type) and UGe (ThIn-type) as well as for the ferromagnetic binaries U3Ge5−x (x=0.2) and UGe2−x (x=0.3) (with TC=94 and 47K) having defect crystal structures of the AlB2- and ThSi2-type, respectively. The obtained data were compared to those of other uranium germanides which have been earlier studied: UGe2 (ZrGa2) and UGe3 (Cu3Au). Among all these germanides, only UGe exhibits enhanced electronic specific heat coefficient, γ(0), equal to 137mJ/molUK2. This value can be compared to that derived for the most known spin fluctuator, UAl2 (143mJ/molUK2). The other uranium germanides have less enhanced γ(0) values (27–65mJ/molUK2). The lowest value of about 20mJ/molUK2 was reported earlier for the typical temperature independent paramagnet UGe3. For the ferromagnetic new phase UGe2−x the inferred magnetic entropy, Sm, reaches at the Curie temperature, TC, a value of Rln2 which corresponds to a doublet ground state of the uranium ion in this deficit digermanide.
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关键词
Actinide compound,Heat capacity,Spin fluctuator,Mixed-valence compound
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