Berlin 2018 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 21: Poster I

MA 21.71: Poster

Dienstag, 13. März 2018, 09:30–13:00, Poster A

Magnetic properties of chain antiferromagnets KFeS₂ and RbFeSe₂ — •Zakir Seidov^1,2, Vladimir Tsurkan³, Hans-Albrecht Krug von Nidda¹, Irina Filipova³, Dorina Croitori³, Axel Günther¹, Airat Kiiamov⁴, Lenar Tagirov^4,5, Farit Vagizov⁴, Tatyana Gavrilova⁵, and Alois Loidl¹ — ¹EP V, EKM, University of Augsburg, D-86135 Augsburg — ²Institute of Physics, ANAS, AZ-1143 Baku — ³Institute of Applied Physics, Academy of Sciences of Moldova, MD-20208 Chisinau — ⁴Institute of Physics, Kazan Federal University, RUS-420008 Kazan — ⁵E.K.Zavoisky Physical-Technical Institute, RAS, RUS-420029 Kazan

The ternary iron chalcogenides KFeS₂ and RbFeSe₂ consisting of chains of edge-sharing FeX₄ (X = S, Se) tetrahedra have been investigated by means of magnetic susceptibility, specific heat, Mössbauer, and ESR measurements. The single crystals exhibit collinear antiferromagnetic (AFM) order with strongly reduced moments below 252 K and 248 K, respectively. For both compounds the small anomaly in C(T) and the corresponding low value of entropy at T_N indicate a significant spin reduction and the existence of AFM fluctuations even far above T_N. Mössbauer parameters determined in the entire temperature range indicate that iron in RbFeSe₂ is in ferric (trivalent) state having strong covalent bonding to selenium ligands. The measured hyperfine field of 216 kOe at 4.2 K is quite reduced as compared to that in high-spin ferric compounds corroborating the strong spin reduction of Fe³⁺. The high-temperature susceptibility data of KFeS₂ and RbFeSe₂ suggest a one-dimensional metallic character along the chains.