Structural and magnetic properties of UFe6Ga6

Abstract

UFe 6 Ga 6 polycrystalline samples were prepared by arc-melting, and single crystals were grown by the Czochralski method. This compound crystallizes in the orthorhombic ScFe 6 Ga 6 -type structure (space group Immm, aZ5.0560(4), bZ8.5484(7) and cZ8.6914(7) Å ), an ordered variant of the ThMn 12 -type structure. A ferromagnetic-type transition at T C Z530(5) K is seen in the magnetization and A.C.-susceptibility measurements, and no other magnetic anomaly is observed down to 5 K. Single crystal magnetization measurements along the three different crystallographic axes indicated a as the easy direction, with a spontaneous magnetization M S Z12.3 m B /f.u. at 5 K. The analysis of the 57 Fe Mössbauer spectroscopy data indicated magnetic hyperfine fields, B hf , significantly lower on 4f sites than on 8k sites, in agreement with the trend already observed on UFe x Al 12Kx , where the average B hf were found to increase with the iron-iron interatomic distances. q

Crystal structure and magnetic properties of UFe5Ga7

“…All this means that the minor phase cannot be the cause of the unidentified X-ray peaks, which thus are assumed to originate from the main phase. The tendency to stabilize superstructures was already observed before in this solubility range for the UFe 6 Ga 6 composition, which does not crystallize in the ThMn 12 -type structure but with the ordered mmm-symmetry [20]. The existence of a superstructure does not allow any Rietveld refinement of the data, but considering the ThMn 12 -type structure the refinement of the UFe 5 Ga 7 lattice parameters results in a = 8.6309 Å and c = 5.0524 Å.…”

“…For UFe 5 Ga 7 , the Curie temperature obtained with this procedure amounts to 439(3) K. Similar to other metallic ferromagnets, the inflection point of the magnetization increases with applied field strength, and for instance, attains a value of 450 K in a field of 0.5 T. Clearly, the Curie temperature for UFe 5 Ga 7 is higher than the ordering temperatures found before for UFe 5 Al 7 , 262(5) K [4] and 268 K [1], and is even higher than that obtained for UFe 7 Al 5 , ferromagnetic below 363 K [3]. However, it is comparable with that observed for UFe 6 Ga 6 , T C = 530(5) K [20].…”

Development of a CALPHAD Thermodynamic Database for Pu-U-Fe-Ga Alloys

“…They are UFeGa [77], UFeGa 5 , [78-81] UFe 6 Ga 6 [82], UFe 5 Ga 7 [83], U 2 FeGa 8 [84] and U 4 FeGa 12 [85]. The crystal structures of these phases have been investigated and low temperature experiments (up to 25 • C), including heat capacity, magnetic susceptibility and electrical resistivity have been performed [77][78][79][80][81][82][83][84][85]. There is no known information on phase stability above room temperature and a thermodynamic assessment with the given information is not possible.…”