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arXiv · 0807.4441

Magnetic Ordering and Negative Thermal Expansion in PrFeAsO

S. A. J. Kimber·D. N. Argyriou·F. Yokaichiya·K. Habicht·S. Gerischer·T. Hansen·T. Chatterji·R. Klingeler·C. Hess·G. Behr·A. Kondrat·B. Buechner
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Abstract

We report the structure and magnetism of PrOFeAs, one of the parent phases of the newly discovered Fe-As superconductors, as measured by neutron powder diffraction. In common with other REOFeAs materials, a tetragonal-orthorhombic phase transition is found on cooling below 136 K and striped Fe magnetism with $k =$(1,0,1) is detected below $\sim$ 85 K. Our magnetic order parameter measurements show that the ordered Fe moment along the a axis reaches a maximum at $\sim$ 40 K, below which an anomalous expansion of the c axis sets in, which results in a negative thermal volume expansion of 0.015 % at 2 K. We propose that this effect, which is suppressed in superconducting samples, is driven by a delicate interplay between Fe and Pr ordered moments.

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S. A. J. Kimber, D. N. Argyriou, F. Yokaichiya, K. Habicht, S. Gerischer, T. Hansen, T. Chatterji, R. Klingeler, C. Hess, G. Behr, A. Kondrat, B. Buechner. 2008-07-28. Magnetic Ordering and Negative Thermal Expansion in PrFeAsO. https://doi.org/10.1103/physrevb.78.140503

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