UFe6Ge6: a new ternary magnetic compound

Crystal structure, 57Fe Mössbauer spectroscopy and magnetization of UxFe6Sn6 (0≤x≤0.6)

“…On the other hand, a ferromagnetic-like transition at approximately 200 K is observed, which suggests that U orders at a temperature much higher than the R elements in RFe 6 X 6 [9]. Furthermore, the Mössbauer spectra of UFe 6 Ge 6 are consistent with the parallel alignment of the m Fe along the [001] direction [16]. Recently, the U-Fe-Sn phase diagram study showed the stabilization of the U x Fe 6 Sn 6 (x!0.6) intermetallics at 750 8C [17].…”

“…In this compound, with the lowest R content and the only case where m Fe is parallel to the (001) plane, B hf are lower, within the range 17.2-20.2 T [14], although still higher than in U x Fe 6 Sn 6 . In the isostructural A x Fe 6 Ge 6 series the U compound also shows the lowest B hf [12,16,24]. Furthermore, in other series of isostructural U-and R-containing compounds, such as A 2 Fe 12 Al 5 [25] and AFe x Al 12Kx [3,4,20], the observed B hf are lower in the U-containing compounds, except in the case of AFe 4 Al 8 where they are similar.…”

“…While in UFe 6 Ge 6 a ferromagnetic transition was observed around 200 K [16], in the U x Fe 6 Sn 6 compounds no clear magnetic transition is detected between room temperature and 2 K. On the other hand, the susceptibilities of the U x Fe 6 Sn 6 compounds increase below their Néel temperature, and for xR0.4 they are characterized by small spontaneous magnetizations as in the R x Fe 6 Sn 6 compounds [13]. In the U-containing compounds, the complex behaviour of their macroscopic global magnetization may be explained by the presence of microdomains with different superstructures and perhaps also with slightly different concentrations of U.…”

“…The metallic radius of U is smaller than the radii of the R atoms and the more delocalized nature of the 5f electrons in U as compared to the 4f in R may have a significant influence both in the easy direction and in the magnitude of the m Fe . Magnetization data and 57 Fe Mössbauer data of UFe 6 Ge 6 show an antiferromagnetic ordering of the Fe atoms at a temperature of 322 K [16], significantly lower than in FeGe or in the RFe 6 Ge 6 intermetallics. On the other hand, a ferromagnetic-like transition at approximately 200 K is observed, which suggests that U orders at a temperature much higher than the R elements in RFe 6 X 6 [9].…”

Crystallographic and magnetic properties of UFe5.8Al6.2 single crystals

“…Ge crystallises in one of these hexagonal structures [20]). We have successfully used the twin-law to refine the crystal structure from the neutron intensities, using the twinning refinement option of the least-squares program SHELXL93 [21].…”