Magnetic Susceptibility of Semiconducting and Metallic FeSi₂

Abstract

In the preceding short note (1) the metal-to-semiconductor phase transition of

Protected Fe valence in quasi-two-dimensionalα-FeSi2

“…In particular, there is no suggestion of magnetic order below room temperature. These results are qualitatively consistent with data previously reported on polycrystalline samples [9]. We have extracted and fitted the low-temperature paramag-netic tail, χ CW (T ) to a Curie-Weiss expression (the fit is shown in Fig.…”

“…The orthorhombic form, β-FeSi 2 , is stable at room temperature and was characterized as a wide gap semiconductor [6]. In contrast, the much simpler tetragonal structure, α-FeSi 2 , is metallic and only stable above 965 o C. α-FeSi 2 can, however, be studied at room temperature and below by quenching the material from high temperatures, and a few crystal structure [7,8], magnetic susceptibility [9], heat capacity [10], and Mössbauer spectroscopy [11,12] measurements carried out on a variety of single crystal and polycrystalline samples exist. However no detailed single-crystal study has been performed to date.…”

Iron group impurities in Β-FeSi2sstudied by EPR

“…This implies that intrinsic ␤-FeSi 2 is diamagnetic in accordance with our EPR spectra of the impurities, which otherwise were not understandable, especially the observed spin states, the relatively narrow lines, and the independence of their resonance fields against temperature changes as well as magnetic-field reversals. The diamagnetism was already concluded from magneticsusceptibility measurements of powder-metallurgically prepared samples 18 as well as single crystals; 19 in both cases paramagnetic contributions were interpreted to arise from imperfections, impurities, and thermally excited carriers. Furthermore, Mössbauer investigations gave no hints of magnetic ordering.…”

Strong Facet-Induced and Light-Controlled Room-Temperature Ferromagnetism in Semiconducting β-FeSi2 Nanocubes

“…As an environmentally friendly semiconductor, beta-phase iron disilicide (β-FeSi 2 ) has been widely investigated in optoelectronics and photovoltaic applications. − There are several techniques to fabricate β-FeSi 2 , for instance, ion beam synthesis, reactive deposition epitaxy, magnetron sputtering, molecular beam epitaxy, chemical vapor deposition (CVD), , and high-temperature reduction in a solution phase and most of the previous studies have focused on the fabrication of thin films or nanoparticles. β-FeSi 2 samples without magnetic dopants prepared by powder metallurgy show diamagnetism at low temperature and Hall effect measurements of β-FeSi 2 polycrystalline films reveal that ferromagnetism is attained only at a temperature below 100 K . The saturation magnetization values of both n-type and p-type β-FeSi 2 , are also quite small (1 × 10 –3 emu/g) .…”

“…11−14 There are several techniques to fabricate β-FeSi 2 , for instance, ion beam synthesis, 15 reactive deposition epitaxy, 16 magnetron sputtering, 17 molecular beam epitaxy, 18 chemical vapor deposition (CVD), 19,20 and high-temperature reduction in a solution phase 21 and most of the previous studies have focused on the fabrication of thin films or nanoparticles. β-FeSi 2 samples without magnetic dopants prepared by powder metallurgy show diamagnetism at low temperature 22 and Hall effect measurements of β-FeSi 2 polycrystalline films reveal that ferromagnetism is attained only at a temperature below 100 K. 23 The saturation magnetization values of both n-type and p-type β-FeSi 2 24,25 are also quite small (1 × 10 −3 emu/g). 26 Ni-or Crdoped β-FeSi 2 single crystals have been reported to have small saturation magnetization at different temperature but there is a ferromagnetic signature at a low temperature.…”