Speaker
Dr
Mathieu Pasturel
(Sciences Chimiques de Rennes)
Description
Several binary or ternary uranium based germanides have been reported to exhibit superconductivity at low temperatures, that emerges either from paramagnetic state (e.g. U7Ge, U5Ge3 [1]) or from ferromagnetically ordered state, in ambient pressure conditions (e.g. URhGe [2], UCoGe [3]) or under applied hydrostatic pressure (e.g. UGe2 [4]). In the search for other germanides with interesting physical properties, we have recently focused on the ternary system U-Ru-Ge. So far, crystal structures and physical properties of four phases from this system have been reported, namely for: U4Ru7Ge6 [5], U3Ru4Ge13 [6], URuGe [7] and U2Ru3Ge [8].
In the present contribution we report on our discovery of two novel compounds: URu1-xGe2 and U34Ru4 xGe33. The crystal structures of both phases have been determined by means of single crystal X-ray diffraction. The former phase crystallizes with a monoclinic unit cell of lattice parameters a = 4.098(1) Å, b = 15.936(2) Å, c = 4.045(1) Å and = 90.09(1)°, which is a derivative of the orthorhombic CeNi1-xSi2 type structure. The other compound adopts a tetragonal structure of the U34Fe4-xGe33 type [a = 10.8933(1) Å and c = 25.3401(3) Å], which may be derived from the binary USi-type unit cell.
The physical properties of both compounds have been studied by means of dc- and ac-magnetization, electrical resistivity and specific heat measurements. Both germanides have been found to order ferromagnetically at Tc = 62(1) K and 38.5(5) K, for URu1-xGe2 and U34Fe4-xGe33, respectively. The obtained results will be comprehensively discussed at the conference with respect to some characteristic structural features, and in comparison to the physical properties of related compounds.
References
[1] Y. Onuki et al., J. Phys. Soc. Jpn., 61, 293 (1992).
[2] D. Aoki et al., Nature, 413, 613 (2001).
[3] N.T. Huy et al., Phys. Rev. Lett., 99, 067006 (2007).
[4] S.S. Saxena et al., Nature, 406, 587 (2000).
[5] B. Lloret et al., J. Magn. Magn. Mater., 67, 232 (1987).
[6] B. Lloret et al., J. Phys., 49 C8, 487 (1988).
[7] R. Troć et al., J. Magn. Magn. Mater., 73, 389 (1988).
[8] A. Vernière et al., J. Alloys Compd., 209, 251 (1994).
Author
Dr
Mathieu Pasturel
(Sciences Chimiques de Rennes)
Co-authors
Dr
Adam Pikul
(INTiBS-PAN)
Dr
Dariusz Kaczorowski
(INTiBS-PAN)
Dr
Henri Noël
(SCR/CSM)
Dr
Olivier Tougait
(SCR/CSM)
