M. Kuznietz et al., THE (U(1-X)LN(X))CO2GE2 SYSTEMS - PARALLEL (LN=ND) AND ANTIPARALLEL (LN=TB) MAGNETIC F-MOMENTS IN THE ORDERED STATE, DETERMINED BY NEUTRON-DIFFRACTION, Physica. B, Condensed matter, 230, 1997, pp. 102-104
The relative orientation of magnetic moments of uranium (5f-atom) and
a lanthanide (Ln, 4f-atom), occupying randomly the same site, was inve
stigated by neutron diffraction in the ordered state of the systems (U
(1-x)Ln(x))Co2Ge2 with light (Ln = Nd) and heavy (Ln = Tb) lanthanide.
These materials crystallize in the ThCr2Si2-type structure. Most of t
hem order in the antiferromagnetic AF-I structure, with alternate (+ -
) stacking of (U, Ln) planes having net moment, and f-moments along th
e tetragonal axis. It is found that the U and Nd moments in (U1-xNdx)C
o2Ge2 are parallel, while the U and Tb moments in (U1-xTbx)Co2Ge2 are
antiparallel. This is apparently due to in-plane direct exchange betwe
en f-atoms, in agreement with the ''spin-charge'' concept, considering
that the U moments behave like light Ln.