Exploring the magneto-volume anomalies in Dy2Fe17 with unconventional rhombohedral crystal structure.

We have synthesized the Dy2Fe17 alloy with an unconventional crystal structure (R (3) over barm space group). Neutron powder thermo-diffraction and X-ray powder diffraction under high pressure (up to 15 GPa) show that the rhombohedral crystal structure is stable. Likewise, the alloy with the usual hexagonal crystal structure (P6(3)/mmc), the rhombohedral variant of Dy2Fe17 compound, exhibits a collinear ferrimagnetic order below the Curie temperature (T-C approximate to 363 K), with antiparallel mutual alignment of the Dy and Fe sublattices. Additionally, we have observed two distinctive issues related to magneto-volume anomalies: (i) the pressure dependence of the cell volume at room temperature shows the existence of a critical pressure at which the compound is no longer ferrimagnetic; and (ii) the cell volume shows invar-like behaviour in a wide temperature range (2-290 K), with a minimum at T approximate to 380 K. The spontaneous volume magnetostriction reaches omega(S) = 1.6 x 10(-2) at 2 K that decreases to zero at T approximate to 500 K (approximate to 1.4 T-C), which is associated with the existence of shortrange magnetic correlations. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.