High pressure induced spin state crossover in Sr2CaYCo4O10.5
V Sikolenko1, I Troyanchuk, M Bushinsky
1Helmholtz-Zentrum Berlin, 14109 Berlin, Germany. Joint Institute for Nuclear Research, 141980 Dubna, Russia. Institute of Applied Geosciences, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
Abstract:
The layered cobaltite Sr(2)CaYCo(4)O(10.5) with formal average cobalt oxidation state close to 3+ has been studied as functions of both temperature and pressure up to 4 GPa by neutron powder diffraction (NPD). The crystal structure is shown to have tetragonal symmetry (space group I4/mmm; 2a(p) × 2a(p) × 4a(p) superstructure), and the magnetic structure at ambient pressure is found to be G-type antiferromagnetic with TN close to 310 K. The magnetic moments within the CoO(6) octahedral layers and anion-deficient CoO(4.5) layers are 1.2μ(B) and 2.8μ(B), respectively. At 25 K, and applied pressure of 3.5 GPa is sufficient to completely suppress a long-range magnetic order. This result is interpreted in terms of a pressure-induced high-to-low spin state crossover of the Co(3+) ions.
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