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arXiv · 1212.5925

Spin-state transition in the Fe-pnictides

H. Gretarsson·S. R. Saha·T. Drye·J. Paglione·Jungho Kim·D. Casa·T. Gog·W. Wu·S. R. Julian·Young-June Kim
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Abstract

We report a Fe Kβx-ray emission spectroscopy study of local magnetic moments in the rare-earth doped iron pnictide Ca_{1-x}RE_xFe_2As_2 (RE=La, Pr, and Nd). In all samples studied the size of the Fe local moment is found to decrease significantly with temperature and goes from ~0.9 μ_B at T = 300 K to ~0.45 μ_B at T = 70 K. In the collapsed tetragonal (cT) phase of Nd- and Pr-doped samples (T<70K) the local moment is quenched, while the moment remains unchanged for the La-doped sample, which does not show lattice collapse. Our results show that Ca_{1-x}RE_xFe_2As_2 (RE= Pr and Nd) exhibits a spin-state transition and provide direct evidence for a non-magnetic Fe^{2+} ion in the cT-phase, as predicted by Yildirim. We argue that the gradual change of the the spin-state over a wide temperature range reveals the importance of multiorbital physics, in particular the competition between the crystal field split Fe 3d orbitals and the Hund's rule coupling.

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H. Gretarsson, S. R. Saha, T. Drye, J. Paglione, Jungho Kim, D. Casa, T. Gog, W. Wu, S. R. Julian, Young-June Kim. 2012-12-24. Spin-state transition in the Fe-pnictides. https://doi.org/10.1103/physrevlett.110.047003

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