Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 14: Poster: Schichten(1-31), Spinabh.Trsp.(32-47), Exch.Bias(48-54), Spindyn.(55-64), Mikromag.(65-76), Partikel(77-88), Oflmag.(89-92), Spinelektr.(93-98), Elektr.Theo.(99-103), Mikromag+PhasÜ+Aniso.(104-122), MagnMat.(123-134), Messm+Mol-Mag.(135-139), Kondo(140-151)

MA 14.113: Poster

Dienstag, 25. März 2003, 15:15–19:15, Zelt

Structural and magnetic properties of NaFe₄Sb₁₂ and KFe₄Sb₁₂ — •Andreas Leithe-Jasper¹, Walter Schnelle¹, Narayani Senthilkumaran¹, Annegrit Rabis¹, Andrei Gippius^1,2, Michael Baenitz¹, and Yuri Grin¹ — ¹MPI für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, D-01187 Dresden, Germany — ²Moscow State University, Faculty of Physics, Russia

Alkali metal iron antimonides NaFe₄Sb₁₂ and KFe₄Sb₁₂ with filled skutterudite structure have been synthesized. Chemical analysis of bulk and EPMA of single crystalline material confirm the stoichiometric composition. Powder XRD data give cubic (space group Im3) lattice parameters a = 9.1767(5) Å for NaFe₄Sb₁₂ and a = 9.1994(5) Å for KFe₄Sb₁₂, respectively. Single crystal XRD analysis of NaFe₄Sb₁₂ (R = 0.027) corroborates full occupancy of the Na 2a position inside the large voids formed by tilted [FeSb₆] octahedra. Similar to other filling atoms in skutterudite structures [1] the Na atoms show a large displacement parameter. The complex interplay of the parent iron-antimony based polyanionic substructure [Fe₄Sb₁₂⁻] with the filler cations Na⁺ and K⁺ gives rise to interesting physical properties. Ferromagnetic order with µ_sat/Fe-atom ≈ 0.4 µ_B is found in both compounds at T_C ≈ 85 K while no magnetic order is found in isostructural Ba and Ca compounds [1]. A paramagnetic effective moment of 1.6–1.8 µ_B/Fe-atom and Θ ≈ T_C is found in the alkali-filled compounds. Metallic conductivity with ρ≈ 1200 µΩ cm at 300 K with a kink at T_C is observed. Heat capacity measurements reveal a small peak at T_C and confirm the bulk character of the ferromagnetism.

[1] C. Uher, Semiconductors and Semimetals 68, 139 (2001).