Electronic, magnetic, and transport properties of the isotypic aluminides SmT₂Al₁₀(T= Fe, Ru)

Abstract

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.

Incommensurate-commensurate magnetic phase transition inSmRu2Al10

“…Figure 4 shows the temperature dependence of magnetic specific heat and entropy at zero field, which almost reproduces the data reported in Ref. 24. The large λ-type anomaly in C mag (T ) at T N reflects the magnetic ordering.…”

“…Basic properties of this compound using a polycrystalline sample has been reported recently. 24 We report the results of electrical resistivity, magnetic susceptibility, and specific heat measurements using a single crystalline sample. It is shown that successive phase transitions take place at T N =12.3 K and at T M =5.6 K, which confirms the previous report.…”

Valence state of Sm in single-crystalline EuO thin films

“…The speciality of samarium arises from the perpetual competition between its two stable valence states: nonmagnetic Sm 2+ and a magnetic Sm 3+ , which is stabilized in many solids by the formation of spatially homogenous non-integral intermediate valence Sm 2.x+ . Experimental examples of samarium containing intermediate valence compounds include the extensively studied SmB 6 [5,6]; high-pressure golden-phases of SmS, SmSe and SmTe [7]; ambient SmO [8]; SmFe 2 Al 10 [9]; Sm 2.75 C 60 [10]; and elemental samarium metal itself [11]. The intermediate valence state of samarium can be understood as an intra-atomic promotion of 4f electrons to 5d bands, going from Sm 2+ (4f 6 5d 0 ) to Sm 3+ (4f 5 5d 1 ).…”

Field-insensitive heavy fermion features and phase transition in the caged-structure quasi-skutterudite Sm3 Ru4 Ge13

“…The χ(T ) behavior is qualitatively different from other Sm-based systems like SmFe 2 Al 10 where strong valence fluctuations have been reported [46]. However a simple Curie-Weiss description was not suitable for Sm 3 Ru 4 Ge 13 and van Vleck terms in the total magnetic susceptibility were required to fit the data.…”

“…The high temperature magnetic susceptibility of Sm compounds can have significant contributions from van Vleck terms [45]. The fact that valence fluctuations and crystal field effect contributions play a role in the magnetic susceptibility of Sm-based intermetallics is shown in the case of SmFe 2 Al 10 and SmRu 2 Al 10 [46]. The 1/χ(T ) plot of SmFe 2 Al 10 showed a broad plateau-like region signifying the underlying valence fluctuation of the Sm 3+ ions; however, such a feature is absent in the present Sm-compound.…”