Magnetism and structure of near-stoichiometric Tm2Fe17+δ compounds

• The Tm2Fe16–Tm2Fe19 compounds are crystallized in the LuFe9.5-type structure.
• The lattice parameters c increases and a decreases as Fe content increases.
• The Néel temperature, spontaneous magnetization, and magnetic anisotropy increase.
• The temperature of ferromagnetic ordering, Tsr and critical field of FOMP decrease.
• The increase of occupation of defected Fe(4e) site causes all these regularities.

Magnetic and structural properties of the Tm2Fe16, Tm2Fe17, Tm2Fe18, and Tm2Fe19 intermetallic compounds were studied. Magnetic measurements, microprobe analysis, X-ray and neutron diffraction investigations were used. The compounds crystallize in a disordered variant of the hexagonal Th2Ni17-type structure. The lattice parameter c increases and lattice parameter a decreases as Fe content increases in the system. The temperatures of ferromagnetic ordering and spin-reorientation and the critical field of the FOMP decrease, whereas the Néel temperature, the spontaneous magnetization, and the magnetic anisotropy increase in the system. The increase of occupation of the defected “dumbbell” Fe(4e) site is likely to cause these regularities.

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