Magnetic Properties of New Filled Skutterudite Compounds EuT₄As₁₂(T=Fe, Ru, and Os) Synthesized under High Pressure

Abstract

New As-based filled skutterudite compounds EuT 4 As 12 (T ¼ Fe, Ru, and Os) have been synthesized under high pressure; these compounds have lattice constants of 8.3374, 8.5120, and 8.5504 Å , respectively, which are larger than those expected from the lanthanide contraction in trivalent ions. The large lattice constants and effective magnetic moments (6.9 -8.3 B /Eu) of the compounds suggest that Eu ions in the compounds are in a divalent or mixed-valent state. Magnetic measurements reveal that EuFe 4 As 12 and EuOs 4 As 12 exhibit ferromagnetic-like phase transitions at 152 and 25 K, respectively. By contrast, EuRu 4 As 12 shows no anomaly down to 2 K. The reciprocal susceptibility À1 of EuFe 4 As 12 has a nonlinear temperature dependence, which implies that the compound has a canted ferromagnetic or ferrimagnetic structure below 152 K. Furthermore, magnetization measurements of EuFe 4 As 12 show that its magnetic moment is about 4.5 B /Eu at 2 K, which is much less than the magnetic moment (7 B /Eu) expected for Eu 2þ . The unexpectedly high transition temperature of 152 K in EuFe 4 As 12 could be related to the interaction of Eu 4f moments with the ferromagnetic [Fe 4 As 12 ] host lattice.

Crossover and coexistence of superconductivity and antiferromagnetism in the filled-skutterudite system Pr1−xEuxPt4Ge12

“…The low T N value for EuPt 4 Ge 12 is possibly due to absence of a magnetic moment on Pt in the Pt-Ge cage, leading to a decrease of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the Eu 2+ localized magnetic moment and the conduction electron spins [19,22]. This is seen in previous reports for the compounds EuRu 4 X 12 with non-magnetic Ru-X cages (ferromagnetic transition temperature, T m ∼ 3.3 K for X = Sb and no magnetic anomaly down to 2 K for X = As) [20,21,23]. In addition, EuPt 4 Ge 12 has a large Sommerfeld coefficient, γ ∼ 220 mJ/mol K, which has been attributed to Eu 2+ spin fluctuations [19,24].…”

“…The value of T N for EuPt 4 Ge 12 is fairly low compared to other Eu-based filled-skutterudite compounds with the Eu 2+ electronic configuration. For example, the compounds EuFe 4 X 12 (X = Sb, As) are ferromagnetic with Curie temperatures, T c ∼ 88 K and ∼ 152 K, respectively, where the enhanced T c has been attributed to the existence of a small magnetic moment (∼ 0.21 µ B for the Fe-Sb cage) on the Fe ion [20,21]. The low T N value for EuPt 4 Ge 12 is possibly due to absence of a magnetic moment on Pt in the Pt-Ge cage, leading to a decrease of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the Eu 2+ localized magnetic moment and the conduction electron spins [19,22].…”

Electron transport and magnetic properties of the filled skutterudite compound ThFe4As12

“…For completeness, we note that in the series MFe 4 As 12 with M being La, Ce, Pr, Nd, Sm, and Eu [17,18,19], magnetism due to itinerant Fe-3d electrons is only not observed in CeFe 4 As 12 , as mentioned above. In all other These compounds were derived from the binary pnictides TX 3 , the prototype of which is CoAs 3 , a diamagnetic zero gap semiconductor [22].…”

Ferrimagnetism in EuFe4As12 revealed by Eu153 NMR and Ding1, Lee2, Nishine3 et al. 2020Phys. Rev. B0000View full textAdd to dashboardCite

“…It is pointed out that the transition temperature of T C ∼ 152 K is relatively high in comparison with other related compounds [11]. When Fe is replaced by Ru or Os, the magnetic ordering temperature is suppressed to 25 K for EuOs 4 As 12 and no magnetic order is observed down to 2 K in EuRu 4 As 12 [11]. On the other hand, when Eu 2+ is replaced by other divalent Sr or Ba ions, no magnetic order is observed although ferromagnetic spin fluctuations were reported [13][14][15].…”