SKM 2023 – scientific programme
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MA: Fachverband Magnetismus
MA 40: Poster Magnetism II
MA 40.14: Poster
Thursday, March 30, 2023, 14:00–16:00, P2/EG
Spin reduction in the covalent chain antiferromagnets RbFeSe2 and KFeS2 — •Z. Seidov1, H.-A. Krug von Nidda1, A. Kiiamov2, M. Kuznetsov2, V. Tsurkan2,3, I. Filippova3, D. Croitori3, F. Mayr1, S. Widmann1, F. Vagizov2, D. Tayurskii2, and L. Tagirov2 — 1EPV, EKM, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany — 2Kazan, Russia — 3Institute of Applied Physics, MD-20208 Chisinau, Moldova
SQUID susceptibility, Mössbauer and specific-heat measurements show that RbFeSe2 and KFeS2 exhibit antiferromagnetic order below TN = 248 K and TN = 251 K, respectively. The magnetic specific heat and the spin state of the Fe3+ ions in the compounds have been analyzed. Phonon dispersion and phonon density of states (PDOS), were evaluated from first-principles calculations. Analysis of our Mössbauer data, utilizing the calculated Fe PDOS, as well as our optical absorption measurements have shown full agreement with the location of the high-frequency optical-type lattice vibrations within the FeX4 (X = S, Se) tetrahedra. The phonon contribution to the heat capacity has been calculated from the PDOS and subtracted from the experimental data to extract the magnetic specific heat of the quasi 1D antiferromagnetically correlated Fe3+ ion chains. The corresponding magnetic entropy suggests a reduced spin value for the Fe3+ ions in both compounds, which seems to be close to an intermediate spin state S = 3/2 in RbFeSe2 and to a low-spin state S = 1/2 in KFeS2.