Investigation of ferromagnetic filled skutterudite compounds EuT₄Sb₁₂(T = Fe, Ru, Os)

Abstract

The physical properties of single crystals of filled skutterudite compounds EuT 4 Sb 12 (T = Fe, Ru, Os) have been investigated by means of x-ray diffraction, electrical resistivity, specific heat, magnetization, and x-ray absorption spectroscopy measurements. The Eu-based materials crystallize in the LaFe 4 P 12 -type structure (space group I m3 appears to exhibit either canted ferromagnetic or ferrimagnetic order at T C = 88 K whereas EuRu 4 Sb 12 and EuOs 4 Sb 12 are ferromagnets with Curie temperatures of T C = 4 and 9 K, respectively. X-ray absorption near edge spectroscopy measurements reveal a nearly divalent Eu electronic configuration for EuT 4 Sb 12 (T = Fe, Ru, Os) with no significant change with T atom or temperature.

Eu2+spin dynamics in the filled skutterudites EuM4Sb12(Garcia1, Adriano2, Cabrera3 et al. 2011Phys. Rev. B4060View full textAdd to dashboardCite

“…The results are g = 1.961(3), for T = Ru, and g = 1.92(1), for T =Os. In addition, at low-T , both values increase, reflecting the internal fields of the low-T ferromagnetic state previously reported for the compounds 15 . These g-values reflect a huge g-shift (∆g = g insulator − g experiment ), which is due to the Exchange interaction with conduction electrons (a polarization effect analogous to the Knight shift in NMR experiments), when compared to g = 1.993(2) found in insulators 21 .…”

“…We should point out, however, that the issue of the Yb valence state in YbFe 4 Sb 12 was subsequently revised in the literature 28 , determining that the Yb ions are in a stable divalent state. In our compounds, no significant fraction of Eu 3+ was found for EuT 4 Sb 12 (T =Ru, Os) nor it was found any sign for temperature dependency of the Eu 2+ fraction in these materials 15 . In EuFe 4 Sb 12 , a fraction of 10 − 15 % of Eu 3+ was reported.…”

“…In these compounds, the filler Eu atom is known to rattle with Einstein temperatures θ E = 78 K (T = Ru) and θ E = 74 K (T = Os) 15,18 . These temperatures are very similar to those where ∆H approaches its maximum before starting to narrow.…”

“…EuT 4 Sb 12 (T = Fe, Ru, Os) are metallic systems that undergo a ferromagnetic transition around T C = 90 K, = 4 K and = 9 K, respectively 15 . Close investigation of the T = Fe system indicates that, in fact, a ferrimagnetic transition takes place at T C = 90 K, as a consequence of an antiferromagnetic coupling of the Eu and Fe moments 16,17 .…”

de Haas–van Alphen Effect in EuRu4Sb12

“…On the other hand, from the recent χ(T ) measurements on the single-crystalline samples, 11 µ eff has been reported to be 8.0µ B /Eu which is close to the expected value for Eu 2+ . The X-ray absorption near edge spectroscopy (XANES) measurements have also revealed a nearly divalent Eu electronic configuration for EuRu 4 Sb 12 .…”