Crystal structure and physical properties ofEu0.83Fe4Sb12

Abstract

Eu 0.83 Fe 4 Sb 12 , was synthesized by arc melting in homogeneous practically single phase form. From Rietveld refinement isotypism was derived with the LaFe 4 P 12 -͑skutterudite͒-type, space group Im 3 , No. 204. The refinement also served to determine the Eu content of xϭ0.83(2). Eu 0.83 Fe 4 Sb 12 orders magnetically below 84 K and isothermal magnetization measurements reveal a spontaneous magnetization reaching about 4.5 B /f.u. at 6 T. The electronic configuration of the Eu ion in this compound appears to be close to the 4 f 7 state, thus behaving almost divalently. From the measurements of transport coefficients, the figure of merit Z was evaluated as ZTϷ0.08 at room temperature. The most outstanding property of this compound, however, is the significant magnetoresistance of about 130% at Tϭ1 K for a magnetic field of 12 T but still 30% near room temperature.

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

“…As displayed in the inset of figure 5, the entropy S = ( C/T ) dT (extrapolating a power law T -dependence of C/T below 0. [10], is S ∼ 27 J mol −1 K −1 , a larger value than expected for Eu 2+ , although consistent with previous results [10]. Figure 5 shows C/T versus T for EuRu 4 Sb 12 and EuOs 4 Sb 12 , which both display a broad maximum below T C (T max ≈ 1.5 and 2.9 K, respectively).…”

“…We have therefore carried out an investigation of single-crystal specimens of EuT 4 Sb 12 (T = Fe, Ru, Os) filled skutterudite compounds. Our results indicate EuFe 4 Sb 12 and EuRu 4 Sb 12 order magnetically at 89 and 4 K, respectively, and their physical properties are generally consistent with those of the polycrystalline samples previously reported [9][10][11]. The physical properties of EuOs 4 Sb 12 have been investigated for the first time; our measurements show that this compound also exhibits ferromagnetic order with a Curie temperature T C = 9 K.…”

“…These values of γ should be considered as an upper limit given the limited fit range and the use of a high temperature extrapolation and are probably more similar to those of LaRu 4 Sb 12 and LaOs 4 Sb 12 [3,18]. It is interesting to note that the γ value of LaFe 4 Sb 12 (γ ∼ 185 mJ mol −1 K −2 [10] and this work) is larger than those for the homologous LaRu 4 Sb 12 and LaOs 4 Sb 12 compounds that have γ = 39, and 36 mJ mol −1 K −2 , respectively [3,18]. Large values of the Sommerfeld coefficient γ ∼ 100 mJ mol −1 K −2 are also observed in the Fe-containing skutterudites NaFe 4 Sb 12 and BaFe 4 Sb 12 , raising the possibility of significant hybridization of the Fe d states with the conduction electrons [19].…”

“…Magnetic measurements on polycrystalline samples of EuFe 4 Sb 12 by Danebrock et al [9] yielded a surprisingly low value of the saturation moment of µ sat = 4.9 µ B /Eu (5 K), compared with the expected value for Eu 2+ (identical to that of Gd 3+ , J = S = 7/2) of M = g J = 7.0 µ B . In addition, after subtracting the magnetic susceptibility of CaFe 4 [10] revealed a partial occupancy of 83% of the Eu sites for this material. Magnetic susceptibility measurements revealed an effective moment µ eff = 7.28 µ B /fu consistent with either the reduced Eu 2+ occupancy or a Eu valence of ν ∼ 2.15 at full Eu site occupancy.…”

“…Magnetic susceptibility measurements revealed an effective moment µ eff = 7.28 µ B /fu consistent with either the reduced Eu 2+ occupancy or a Eu valence of ν ∼ 2.15 at full Eu site occupancy. On the basis of the reduced saturation moment µ sat = 3.55 µ B /Eu (2 K), the authors suggested either canted ferromagnetic or ferrimagnetic order below T C = 84 K for EuFe 4 Sb 12 [10]. From magnetization and specific heat measurements on polycrystalline samples, EuRu 4 Sb 12 was found to order ferromagnetically at T C = 3.3 K with a saturation moment µ sat = 6.2 µ B /Eu (2.1 K) and an effective moment of µ Eu eff = 7.2 µ B /Eu [11].…”