Structure and magnetism of R2T2X compounds
and their hydrides; comparison of lanthanides and actinides
Chem.
Met. Alloys 6
(2013) 170-176
https://doi.org/10.30970/cma6.0255
Ladislav HAVELA, Silvie MAŠKOVÁ, Pavel
SVOBODA, Khrystyna MILIYANCHUK,
Alexandre KOLOMIETS,
Alexander V. ANDREEV
The group of “221” compounds
crystallizing in the Mo2FeB2 structure type comprises
more than 400 members known so far. The onset of magnetic moments and their
ordering can be studied in the actinide representatives by tuning the 5f-ligand hybridization strength,
including detailed investigations of the non-Fermi liquid regime. The mechanism
of specific two-ion anisotropy, depending exclusively on the positions of the
nearest-neighbor U atoms, can be tested due to the variety of coordinations observed within a single structure type.
Possible dimerization of the magnetic structures,
representing a practical realization of a Shastry-Sutherland
lattice, has been the motivation for several studies of rare-earth based
materials, and can be a reason for the tendency to magnetic frustration.
Hydrogen absorption, being an additional degree of freedom for tuning the
physical properties, was found to be limited to 2 H atoms per f.u. in U-based materials. The strengthening of U magnetism
may be attributed to predominant volume expansion and consequent 5f-band narrowing. In several rare-earth
based compounds much higher H absorption has been observed (the limit seems to
be 8 H/f.u.). The structure reacts either by
distortion or amorphization in such cases. H
absorption leads to weakening of the magnetic interactions, probably related to
the reduced concentration of conduction electrons.
Reaction of the R3T tetrahedra
in Mo2FeB2-type R2T2X compounds to H insertion for light (left) and heavy (right) rare
earths.
Keywords
Hydrides / Intermetallic
compounds / Lanthanides / Actinides / Magnetic properties