Abstract
The magnetic studies of EuBaCo2O5.50, EuBaCo1.93O5.40, and EuBaCo1.90O5.36 have been performed. Layered cobaltites EuBaCo2–x O5.5–δ demonstrated the ferrimagnetic ordering in the temperature range 200 K < T < 650 K. The ferromagnetic Curie temperature T C almost did not change as the number of Co3+–O–Co3+ bonds decreased. The contributions of the ferro- and antiferromagnetic interactions were nearly the same and determine the relationship T C > T N and T C < T N. At T > T C, the antiferromagnetic order was retained in the EuBaCo1.90O5.36. As temperature increased, EuBaCo2–xO5.5–δ conserved the IS state in pyramids, and gradual LS → IS → HS transitions occurred in octahedron sites. The increase in the effective magnetic moment μeff in EuBaCo1.90O5.36 at T > 580 K demonstrated the transition of Co3+ ions to the HS state at lower temperatures as compared to the EuBaCo2O5.50 stoichiometric composition, and the structural distortions and the increase in the unit cell volume favored to this transition.
Published Version
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