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

We have synthesized the Dy2Fe17 alloy with an unconventional crystal structure (R3¯m 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 (P63/mmc), the rhombohedral variant of Dy2Fe17 compound, exhibits a collinear ferrimagnetic order below the Curie temperature (TC ≈ 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 ≈ 380 K. The spontaneous volume magnetostriction reaches ωS = 1.6 × 10−2 at 2 K that decreases to zero at T ≈ 500 K (≈1.4 TC), which is associated with the existence of short-range magnetic correlations.