An X-ray, Mössbauer and magnetization investigation of hexagonal FeSe

Amcoff*, T. Ericsson, A. Gismelseed

*المؤلف المقابل لهذا العمل

نتاج البحث: المساهمة في مجلةمقالمراجعة النظراء

4 اقتباسات (Scopus)

ملخص

X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and magnetization (SQUID) data are reported for a “pyrrhotite-like” compound (∂-FeSe), belonging to the central portion of the FeSe system. The ∂-phase(s) extends compositionally over a range of around Feo.94Se-Feo.86Se at 870 K, but narrows around Fe7Se8 at room temperature. Lattice parameters for the primitive hexagonal cell decrease regularly with increasing vacancy concentration x in Fe1-.xSe; c = 5.97 — 5.87 A, a = 3.65 — 3.62 A. An observed regular decrease in cell axes ratio, c/a = 1.644 — 0.145 x, is described as due to increased ordering with increased vacancy concentration. The disordered high-temperature 1 c structure is maintained at room temperature for vacancy-poor compositions, while superstructures, 3c and 4c, form for vacancy-rich compositions. Using a bond model for the magnetic coupling, MS spectra for ordered 3c and 4c superstructures can be well fitted assuming three well-defined surroundings, while those for disordered lc show a distribution in surroundings. A spin direction change, from the c-plane towards the c-axis with decrease in temperature, is sharp at 130 K for 3c, extended and incomplete for 4c (~220 — 120 K), and again rather sharp for lc at ∽ 220 K. It is suggested that the spin flip at 130 K for 3c, which is also visible (but weak) in SQUID measurements of lc samples, is indicative of an element of short range order in the disordered structure.

اللغة الأصليةEnglish
الصفحات (من إلى)197-205
عدد الصفحات9
دوريةZeitschrift fur Kristallographie - New Crystal Structures
مستوى الصوت209
رقم الإصدار3
المعرِّفات الرقمية للأشياء
حالة النشرPublished - 1994
منشور خارجيًانعم

ASJC Scopus subject areas

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