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Zusammenfassung:
We report the results of a comprehensive physical and magnetic property
study of the new isotypic aluminides SmT2Al10 (T = Fe, Ru). These two
compounds are members of a rare-earth based system which has become an
exemplary case study of the interplay of magnetism and correlated
electron phenomena. SmFe2Al10 and SmRu2Al10 are found to order in a
putative antiferromagnetic spin arrangement at T-N = 14.5 K and 12.5 K,
respectively. Moreover, SmRu2Al10 shows a further phase transition at
T-SR = 5 K which is likely due to spin reorientation. The susceptibility
of SmFe2Al10 points to a valence instability of the Sm ionic state at
intermediate temperatures well above T-N. Electronic and thermal
transport confirm that SmFe2Al10 undergoes an antiferromagnetic
superzone gap formation below T-N, whereas SmRu2Al10 suffers a lattice
anomaly driven magnetoelastic coupling at T-N. Below T-N, the physical
properties of SmT2Al10 (T = Fe, Ru) are governed by magnons with an
antiferromagnetic spin-wave spectrum that reveals spin-gap opening. Our
findings in this work have exposed a new anomalous correlated compound
in the RT2Al10 series. SmFe2Al10 has a magnetic ordered ground state in
spite of an unstable valence at higher temperature. This is comparable
with CeRu2Al10, which is a unique and controversial Kondo insulator that
orders antiferromagnetic at T-N = 27 K. Among the series of rare-earth
RT2Al10 compounds, the presented Sm compounds are two new members with
anomalously high magnetic ordering temperatures, and it is envisaged
that together with the two very well studied compounds CeRu2Al10 and
CeOs2Al10 our presented studies will enable a broader approach towards
understanding the fascinating properties of this materials class.
