Role of “Dumbbell” Pairs of Fe in Spin Alignments and Negative Thermal Expansion of Lu₂Fe₁₇-Based Intermetallic Compounds

Abstract

Knowledge of negative thermal expansion (NTE) is an interesting issue in the field of materials science and engineering. It has been proposed that the unique dumbbell pairs of Fe (dumbbells) are highly entangled in the NTE behaviors of R2Fe17 (R = rare earth) compounds but still remain controversial. Here, a facile method is employed to explore the role of dumbbells in spin alignments and NTE by the nonstoichiometric design of Lu2–x Fe17 compounds. The powder synchrotron X-ray diffraction, magnetometry, and neutron powder diffraction investigations indicate that a decrease of the Lu content can enhance the dumbbell concentration and motivate an incommensurate magnetic structure simultaneously. However, increasing the dumbbell concentration makes little difference in the amplitude of the ordered magnetic moments of Fe sublattices, which reveals an equivalent NTE behavior for Lu2–x Fe17 compounds. This work gives insight into the role that dumbbells played in spin alignments and NTE for Lu2Fe17-based compounds, correcting the previously proposed conjecture and probably conducive to adjusting the related magnetic performances of R2Fe17 compounds in the future.

Plastic and low-cost axial zero thermal expansion alloy by a natural dual-phase composite

“…This behavior is especially unusual for metallic materials. Only a few couplings among lattice, spin, and orbital induce a reduced coefficient of thermal expansion by the virtue of the so-called magneto-volume effect 4 – 6 , which has been reported in a few single-phase metallic materials, such as the conventional Invar alloy 7 (Fe 0.64 Ni 0.36 ) and some magnetic intermetallic compounds (e.g., Tb(Co,Fe) 2 8 , La(Fe,Si,Co) 13 9 ). On the other hand, most of these ZTE compounds are brittle with low strength and little ductility 10 – 14 , with concerned applicability due to low fracture toughness.…”

“…Interestingly, on the R-Fe (R = rare earth) binary phase diagram 26 (see Supplementary Fig. 1 ), Fe forms a eutectic system with R 2 Fe 17 —a typical negative thermal expansion (NTE) intermetallic compound driven by magnetic ordering 6 , 27 , 28 . This indicates that the R 2 Fe 17 phase could coexist in equilibrium with Fe at any temperature without losing its own NTE character.…”

A Seawater‐Corrosion‐Resistant and Isotropic Zero Thermal Expansion (Zr,Ta)(Fe,Co)2 Alloy

“…[20,21] Such magnetovolume effects are mainly triggered by magnetic moment of rare earths (Re) or Mn/Fe/Co atoms [22,23] which however have high reactivity under harsh environments. [9,24,25] As a consequence, most newly reported ZTE alloys show an undesirable environmental instability, e.g., La(Fe, Si, A) 13 , [26] Re 2 (Fe, A) 17 , [27] and (Mn, A)(Co, A)Ge [28] (Re: rare-earth metals, A: transition metals). However, some metals are prone to oxidation to form stable oxide films, like Al 2 O 3 , ZrO 2 , etc., which are resistant to harsh environmental erosion.…”

Plastic and low-cost zero thermal expansion alloy by a natural dual-phase composite

“…However, ZTE performance is rare in nature. This behavior is especially unusual for metallic materials: only a few couplings among lattice, spin and orbital induces a reduced coe cient of thermal expansion by virtue of the so-called magneto-volume effect [4][5][6] , which so far has been reported in conventional Invar alloy 7 (Fe 0.64 Ni 0.36 ) and some magnetic intermetallic compounds (e.g., Tb(Co,Fe) 2 8 , La(Fe,Si,Co) 13 9 )…”

“…Interestingly, on the R-Fe (R = rare earth) binary phase diagram 26 (see Fig. S1), Fe forms a eutectic system with R 2 Fe 17 , a typical negative thermal expansion (NTE) intermetallic compound driven by magnetic ordering 6,27,28 . This inspires us that the R 2 Fe 17 phase could coexist in equilibrium with Fe at any temperature without losing its own NTE character.…”