Magnetic anisotropy in FeSb studied by 57Fe Mossbauer spectroscopy

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:399

Article

Komedera, K.¹  Jasek, A. K.¹  Blachowski, A.¹  Ruebenbauer, K.¹  Krzton-Maziopa, A.² 

[1] Pedag Univ, Inst Phys, Mossbauer Spect Div, PL-30084 Krakow, Poland

[2] Warsaw Univ Technol, Fac Chem, PL-00664 Warsaw, Poland

关键词: Magnetic anisotropy;    Iron pnictides;    Mossbauer spectroscopy;   

DOI  :  10.1016/j.jmmm.2015.09.076

来源: Elsevier

【 摘 要 】

The Fe1+xSb compound has been synthesized close to stoichiometry with x=0.023(8). The compound was investigated by Fe-57 Mossbauer spectroscopy in the temperature range 4.2-300 K. The anti-ferromagnetic ordering temperature was found as 232 K i.e. much higher than for the less stoichiometric material. Regular iron was found to occupy two different positions in proportion 2:1. They differ by the electric quadrupole coupling constants and both of them exhibit extremely anisotropic electric field gradient tensor (EFG) with the asymmetry parameter eta approximate to 1. The negative component of both EFGs is aligned with the c-axis of the hexagonal unit cell, while the positive component is aligned with the (120) direction. Hence, a model describing deviation from the NiAs P6(3)/mmc symmetry group within Fe-planes has been proposed. Spectra in the magnetically ordered state could be explained by introduction of the incommensurate spin spirals propagating through the iron atoms in the direction of the c-axis with a complex pattern of the hyperfine magnetic fields distributed within a-b plane. Hyperfine magnetic field pattern of spirals due to major regular iron is smoothed by the spin polarized itinerant electrons, while the minor regular iron exhibits hyperfine field pattern characteristic of the highly covalent bonds to the adjacent antimony atoms. The excess interstitial iron orders magnetically at the same temperature as the regular iron, and magnetic moments of these atoms are likely to form two-dimensional spin glass with moments lying in the a-b plane. The upturn of the hyperfine field for minor regular iron and interstitial iron is observed below 80 K. Magneto-elastic effects are smaller than for FeAs, however the recoilless fraction increases significantly upon transition to the magnetically ordered state. (C) 2015 Elsevier B.V. All rights reserved.

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